Method, apparatus, and system for transmitting or receiving control channel and data channel in wireless communication system

ABSTRACT

A base station of a wireless communication system is disclosed. The base station of the wireless communication includes a communication module, and a processor. The processor generates a preemption indicator indicating a preempted resource. In this case, the resource indicated by the preemption indicator does not include an orthogonal frequency divisional multiplexing (OFDM) symbol configured as an uplink (UL) symbol by a radio resource control (RRC) signal. The processor is configured to transmit the preemption indicator to a user equipment of the wireless system based on a predetermined period.

TECHNICAL FIELD

The present invention relates to a wireless communication system. Morespecifically, the present invention relates to a wireless communicationmethod, apparatus, and system for transmitting and receiving datachannels and control channels.

BACKGROUND ART

The 3rd generation partnership project new radio (3GPP NR) systemimproves the spectral efficiency of the network, enabling operators toprovide more data and voice services over a given bandwidth. As aresult, the 3GPP NR system is designed to meet the demands forhigh-speed data and media transmissions in addition to supporting largevolumes of voice. The advantages of the NR system are supports of highprocessing amount, low latency, frequency division duplex (FDD) and timedivision duplex (TDD) on the same platform, improved end userexperience, and a simple architecture with low operating costs.

For more efficient data processing, a Dynamic TDD of the NR system mayuse a method of varying the number of orthogonal frequency divisionmultiplexing (OFDM) symbols that can be used for uplink/downlinkaccording to data traffic directions of users of a cell. For example,the base station may allocate a plurality of downlink OFDM symbols to aslot (or subframe) when a downlink traffic of the cell is larger than anuplink traffic. The information on the slot configuration should betransmitted to the terminals.

DISCLOSURE Technical Problem

It is an object of the present invention to provide a method andapparatus for efficiently transmitting a signal in a wirelesscommunication system, in particular, a cellular wireless communicationsystem. In addition, it is an object of the present invention to providea method for transmitting and receiving a downlink control channel, anapparatus and a system therefor.

Technical objects desired to be achieved in the present invention arenot limited to the aforementioned objects, and other technical objectsnot described above will be clearly understood by those skilled in theart from the following disclosure.

Technical Solution

According to an embodiment of the present invention, a base station of awireless communication system includes a communication module; and aprocessor configured to control the communication module. The processoris configured to generate a preemption indicator indicating a preemptedresource, and transmit the preemption indicator to a terminal of thewireless communication system based on a predetermined period. In thiscase, the resource indicated by the preemption indicator does notinclude an orthogonal frequency divisional multiplexing (OFDM) symbolconfigured as an uplink (UL) symbol by a radio resource control (RRC)signal.

The OFDM symbol configured to the user equipment may be classified intothe UL symbol for UL transmission, a downlink (DL) symbol for DLtransmission, and a flexible symbol that is not configured as the ULsymbol and the DL symbol.

The RRC signal may be a cell-specific RRC signal commonly applied to acell.

The preemption indicator may divide a plurality of OFDM symbolsindicated by the preemption indicator into a plurality of groups, andindicate whether at least one OFDM symbols is preempted in one or moreOFDM symbols included in each of the plurality of groups for each of theplurality of groups.

The number of the plurality of groups may be predetermined.

When the number of the plurality of groups is N and the number of theplurality of OFDM symbols indicated by the preemption indicator is S,the processor may group the first mod(S,N) groups among the N groupssuch that each of the first mod(S, N) groups includes ceil(S/N) OFDMsymbols, and group the remaining N−mod(S,N) groups such that each of theN−mod(S, N) groups includes floor(S/N) OFDM symbols. mod(a, b) isa−floor(a/b)*b, floor(x) is the largest number among integers less thanor equal to x, and ceil(x) is the smallest number among integers greaterthan or equal to x.

The preemption indicator may be monitored by the terminal in units ofinteger slots.

The number of OFDM symbols between predetermined periods may berepresented by N_symb*T_INT*2^((μ-μ_INT)). N_symb may be the number ofOFDM symbols included in the slot, T_INT may be a period in which theuser equipment monitors the preemption indicator, μ_INT may be a valuesatisfying that the subcarrier spacing of the carrier in which thepreemption indicator is transmitted is 15*2^(μ_INT) KHz, and μ may be avalue satisfying that the subcarrier spacing of the carrier in which thepreemption indicator indicates information on the preemption is 15*2^(μ)KHz. The processor may be configured to configure a values of T_INT, μ,and μ_INT that make N_symb*T_INT*2^((μ-μ_INT)) is a natural number.

The preemption indicator may indicate a full band of the bandwidth part(BWP) used by the user equipment. The BWP may be a frequency band inwhich the user equipment transmits and receives a bandwidth less than orequal to the bandwidth of a carrier configured to the user equipment.

According to an embodiment of the present invention, a user equipment ofa wireless communication system includes a communication module; and aprocessor configured to control the communication module. The processormay be configured to periodically monitor a preemption indicatorindicating a resource preempted from a base station of the wirelesscommunication system, when receiving the preemption indicator, determinethat the resource indicated by the preemption indicator does not includean Orthogonal Frequency Divisional Multiplexing (OFDM) symbol configuredas an uplink (UL) symbol by a radio resource control (RRC) signal,determine a resource in which transmission from the base station to theuser equipment is generated among resources scheduled to the userequipment based on the preemption indicator, and decode data receivedfrom the base station based on the determination of the resource inwhich the transmission from the base station to the user equipmentoccurs.

The OFDM symbol configured to the user equipment is classified into theUL symbol for UL transmission, a downlink (DL) symbol for DLtransmission, and a flexible symbol that is not configured as the ULsymbol and the DL symbol.

The RRC signal may be a cell-common RRC signal commonly applied to acell.

The preemption indicator may divide a plurality of OFDM symbolsindicated by the preemption indicator into a plurality of groups, andthe processor may determine whether transmission from the base stationto the user equipment occurs in at least one OFDM symbol included ineach of the plurality of groups for each of the plurality of groups.

The number of the plurality of groups may be predetermined.

When the number of the plurality of groups is N and the number of theplurality of OFDM symbols indicated by the preemption indicator is S,the processor may determine that each of the first mod(S,N) groups amongthe N groups includes ceil(S/N) OFDM symbols, and each of otherN−mod(S,N) groups includes floor(S/N) OFDM symbols. At this time, mod(a,b) is a−floor(a/b)*b, floor(x) is the largest number among integers lessthan or equal to x, and ceil(x) is the smallest number among integersgreater than or equal to x.

The processor may monitor the preemption indicator in units of integerslots.

The number of OFDM symbols between periods for monitoring the preemptionindicator may be N_symb*T_INT*2_((μ-μ_INT)). N_symb may be the number ofOFDM symbols included in the slot, T_INT may be a monitoring period ofthe preemption indicator, μ_INT may be a value satisfying that thesubcarrier spacing of the carrier in which the preemption indicator istransmitted is 15*2^(μ_INT) KHz, and μ may be a value satisfying thatthe subcarrier spacing of the carrier in which the preemption indicatorindicates information on the preemption is 15*2^(μ) KHz. The processormay be configured to expect values of T_INT, μ, and μ_INT that makeN_symb*T_INT*2^((μ-μ_INT)) is a natural number.

The preemption indicator may indicate the full band of the bandwidthpart (BWP) used by the user equipment, and the BWP may be a frequencyband in which the user equipment transmits and receives a bandwidth lessthan or equal to the bandwidth of a carrier configured to the userequipment.

According to an embodiment of the present invention, a method ofoperating a user equipment of a wireless system includes periodicallymonitoring a preemption indicator indicating a resource preempted from abase station of the wireless communication system, when receiving thepreemption indicator, determining that the resource indicated by thepreemption indicator does not include an Orthogonal Frequency DivisionalMultiplexing (OFDM) symbol configured as an uplink (UL) symbol by aradio resource control (RRC) signal, when receiving the preemptionindicator, determining a resource in which transmission from the basestation to the user equipment is generated among resources scheduled tothe user equipment based on the preemption indicator, and decoding datareceived from the base station based on the determination of theresource in which the transmission from the base station to the userequipment occurs.

The OFDM symbol configured to the user equipment is divided into the ULsymbol for UL transmission, a downlink (DL) symbol for DL transmission,and a flexible symbol that is not configured as the UL symbol and the DLsymbol.

The RRC signal may be a cell-common RRC signal commonly applied to acell.

The preemption indicator may divide a plurality of OFDM symbolsindicated by the preemption indicator into a plurality of groups, andthe determining the resource in which the transmission from the basestation to the user equipment occurs may include determining whethertransmission from the base station to the user equipment occurs in atleast one OFDM symbol included in each of the plurality of groups foreach of the plurality of groups.

Advantageous Effects

A wireless communication system according to an embodiment of thepresent invention, in particular, a cellular wireless communicationsystem provides a method and device for efficiently transmittingsignals. In addition, a wireless communication system according to anembodiment of the present invention provides a wireless communicationmethod and device for transmitting and receiving a downlink controlchannel.

Effects obtainable from various embodiments of the present disclosureare not limited to the above-mentioned effects, and other effects notmentioned above may be clearly derived and understood to those skilledin the art from the following description.

DESCRIPTION OF DRAWINGS

FIG. 1 illustrates an example of a wireless frame structure used in awireless communication system.

FIG. 2 illustrates an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system.

FIG. 3 is a diagram illustrating a physical channel used in a 3GPPsystem and a general signal transmission method using the physicalchannel.

FIG. 4 illustrates an SS/PBCH block for initial cell access in a 3GPP NRsystem.

FIG. 5(a) is a diagram of a procedure for transmitting controlinformation in a 3GPP NR system.

FIG. 5(b) is a diagram illustrating CCE aggregation of PDCCH andmultiplexing of PDCCH.

FIG. 6 is a diagram illustrating a control resource set (CORESET) inwhich a physical downlink control channel (PDCCH) can be transmitted ina 3GPP NR system.

FIG. 7 is a diagram illustrating CCE aggregation search space allocationfor a common search space and a UE specific (or terminal specific)search space.

FIG. 8 is a conceptual diagram illustrating carrier aggregation.

FIG. 9 is a diagram for describing single carrier communication andmulticarrier communication.

FIG. 10 is a diagram illustrating an example in which a cross carrierscheduling technique is applied.

FIG. 11 is a block diagram showing the configurations of a userequipment and a base station according to an embodiment of the presentinvention.

FIG. 12 shows an example of CORESET according to an embodiment of thepresent invention in an NR system.

FIG. 13 shows an example of a BWP configured for a user equipmentaccording to an embodiment of the present invention.

FIG. 14 shows an example of BWP configured for a user equipment andCORESET for BWP according to an embodiment of the present invention.

FIG. 15 shows a method for a user equipment to monitor a preemptionindicator based on a BWP and a CORESET corresponding to the BWPaccording to an embodiment of the present invention.

FIG. 16 shows a method for a user equipment to monitor a preemptionindicator based on a CORESET corresponding to a BWP scheduled with aPDSCH according to an embodiment of the present invention.

FIG. 17 shows a method of monitoring a preemption indicator based on aCORESET corresponding to a BWP scheduled with a PDSCH when a pluralityof BWPs configured for a user equipment overlap each other according toan embodiment of the present invention.

FIGS. 18 and 19 show a method in which a user equipment monitors apreemption indicator based on a predetermined BWP according to anembodiment of the present invention.

FIG. 20 shows a method for a user equipment to monitor a preemptionindicator in a CORESET in which a PDCCH scheduling a PDSCH istransmitted according to an embodiment of the present invention.

FIG. 21 shows an example of a configuration of OFDM symbols included ina slot when TDD is used in a wireless system according to an embodimentof the present invention.

FIG. 22 shows an OFDM symbol indicated by a preemption indicatoraccording to an embodiment of the present invention.

FIG. 23 shows an OFDM symbol indicated by a preemption indicatoraccording to an embodiment of the present invention.

FIGS. 24 to 26 show OFDM symbols indicated by a preemption indicatoraccording to an embodiment of the present invention in relation to areserved resource.

FIG. 27 shows an OFDM symbol indicating whether a bitmap of a preemptionindicator is preempted according to an embodiment of the presentinvention.

FIG. 28 shows an OFDM symbol indicating whether a bitmap of a preemptionindicator is preempted according to another embodiment of the presentinvention.

FIG. 29 shows an OFDM symbol indicating whether a bitmap of a preemptionindicator is preempted according to another embodiment of the presentinvention.

FIG. 30 shows that when a CA is configured to a UE according to anembodiment of the present invention, the user equipment monitors apreemption indicator indicating information on preemption occurring inanother carrier in one carrier.

FIGS. 31 to 32 show a method of operating a base station and a userequipment according to an embodiment of the present invention.

MODE FOR CARRYING OUT THE INVENTION

Terms used in the specification adopt general terms which are currentlywidely used as possible by considering functions in the presentinvention, but the terms may be changed depending on an intention ofthose skilled in the art, customs, and emergence of new technology.Further, in a specific case, there is a term arbitrarily selected by anapplicant and in this case, a meaning thereof will be described in acorresponding description part of the invention. Accordingly, it intendsto be revealed that a term used in the specification should be analyzedbased on not just a name of the term but a substantial meaning of theterm and contents throughout the specification.

Throughout this specification and the claims that follow, when it isdescribed that an element is “connected” to another element, the elementmay be “directly connected” to the other element or “electricallyconnected” to the other element through a third element. Further, unlessexplicitly described to the contrary, the word “comprise” will beunderstood to imply the inclusion of stated elements but not theexclusion of any other elements unless otherwise stated. Moreover,limitations such as “more than or equal to” or “less than or equal to”based on a specific threshold may be appropriately substituted with“more than” or “less than”, respectively, in some exemplary embodiments.

The following technology may be used in various wireless access systems,such as code division multiple access (CDMA), frequency divisionmultiple access (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier-FDMA(SC-FDMA), and the like. The CDMA may be implemented by a wirelesstechnology such as universal terrestrial radio access (UTRA) orCDMA2000. The TDMA may be implemented by a wireless technology such asglobal system for mobile communications (GSM)/general packet radioservice (GPRS)/enhanced data rates for GSM evolution (EDGE). The OFDMAmay be implemented by a wireless technology such as IEEE 802.11 (Wi-Fi),IEEE 802.16 (WiMAX), IEEE 802-20, evolved UTRA (E-UTRA), and the like.The UTRA is a part of a universal mobile telecommunication system(UMTS). 3rd generation partnership project (3GPP) long term evolution(LTE) is a part of an evolved UMTS (E-UMTS) using evolved-UMTSterrestrial radio access (E-UTRA) and LTE-advanced (A) is an evolvedversion of the 3GPP LTE. 3GPP new radio (NR) is a system designedseparately from LTE/LTE-A, and is a system for supporting enhancedmobile broadband (eMBB), ultra-reliable and low latency communication(URLLC), and massive machine type communication (mMTC) services, whichare requirements of IMT-2020. For the clear description, 3GPP NR ismainly described, but the technical idea of the present invention is notlimited thereto.

Unless otherwise specified in this specification, a base station mayrefer to a next generation node B (gNB) as defined in 3GPP NR.Furthermore, unless otherwise specified, a terminal may refer to a userequipment (UE).

This application claims priority to Korean Patent Application Nos.10-2017-0076934 (2017 Jun. 16), 10-2017-0127516 (2017 Sep. 29),10-2017-0129707 (2017 Oct. 11), 10-2017-0149933 (2017 Nov. 10),10-2018-0018903 (2018 Feb. 17), and 10-2018-0040134 (2018 Apr. 6) andthe embodiments and descriptions described in each of the aboveapplications which are the basis of priority are to be included in thedetailed description of the present application.

Unless otherwise specified in this specification, a base station mayrefer to a next generation node B (gNB) as defined in 3GPP NR.Furthermore, unless otherwise specified, a terminal may refer to a userequipment (UE).

FIG. 1 illustrates an example of a wireless frame structure used in awireless communication system.

Referring to FIG. 1, the wireless frame (or radio frame) used in the3GPP NR system may have a length of 10 ms (Δf_(max)N_(f)/100)*T_(c)). Inaddition, the wireless frame includes 10 subframes (SFs) having equalsizes. Herein, Δf_(max)=480*10³ Hz, N_(f)=4096,T_(c)=1/(Δf_(ref)*N_(f,ref)), Δf_(ref)=15*10³ Hz, and N_(f,ref)=2048.Numbers from 0 to 9 may be respectively allocated to 10 subframes withinone wireless frame. Each subframe has a length of 1 ms and may includeone or more slots according to a subcarrier spacing. More specifically,in the 3GPP NR system, the subcarrier spacing that may be used is15*2^(μ) kHz, and μ can have a value of μ=0, 1, 2, 3, 4 as subcarrierspacing configuration. That is, 15 kHz, 30 kHz, 60 kHz, 120 kHz and 240kHz may be used for subcarrier spacing. One subframe having a length of1 ms may include 2^(μ) slots. In this case, the length of each slot is2^(−μ) ms. Numbers from 0 to 2^(μ)−1 may be respectively allocated to2^(μ) slots within one subframe. In addition, numbers from 0 to10*2^(μ)−1 may be respectively allocated to slots within one subframe.The time resource may be distinguished by at least one of a wirelessframe number (also referred to as a wireless frame index), a subframenumber (also referred to as a subframe number), and a slot number (or aslot index).

FIG. 2 illustrates an example of a downlink (DL)/uplink (UL) slotstructure in a wireless communication system. In particular, FIG. 2shows the structure of the resource grid of the 3GPP NR system.

There is one resource grid per antenna port. Referring to FIG. 2, a slotincludes a plurality of OFDM symbols in a time domain and includes aplurality of resource blocks (RBs) in a frequency domain. An OFDM symbolalso means one symbol duration. Unless otherwise specified, an OFDMsymbol may be simply referred to as a symbol. Referring to FIG. 2, asignal transmitted in each slot may be represented by a resource gridconsisting of N^(size, μ) _(grid, x)*N^(RB) _(sc) subcarriers, andN^(slot) _(symb) OFDM symbols. Here, x=DL for the downlink resourcegrid, and x=UL for the uplink resource grid. N^(size, μ) _(grid, x)denotes the number of resource blocks (downlink or uplink according tox) according to a subcarrier spacing configuration μ, and N^(slot)_(symb) denotes the number of OFDM symbols in a slot. N^(RB) _(sc) isthe number of subcarriers constituting one RB and N^(RB) _(sc)=12. AnOFDM symbol may be referred to as a cyclic shift OFDM (CP-OFDM) symbolor a discrete Fourier transform spreading OFDM (DFT-s-OFDM) symbolaccording to a multiple access scheme. The number of OFDM symbolsincluded in one slot may vary according to the length of a cyclic prefix(CP). For example, in the case of a normal CP, one slot includes 14 OFDMsymbols, but in the case of an extended CP, one slot may include 12 OFDMsymbols. In a specific embodiment, the extended CP may only be used at60 kHz subcarrier spacing. In FIG. 2, for convenience of description,one slot includes 14 OFDM symbols by way of example, but embodiments ofthe present invention may be applied in a similar manner to a slothaving a different number of OFDM symbols. Referring to FIG. 2, eachOFDM symbol includes N^(size, μ) _(grid, x)*N^(RB) _(sc) subcarriers inthe frequency domain. The type of subcarrier may be divided into a datasubcarrier for data transmission, a reference signal subcarrier fortransmission of a reference signal, and a guard band. The carrierfrequency is also referred to as the center frequency (fc).

An RB may be defined by N^(slot) _(symb) (e.g., 14) consecutive OFDMsymbols in the time domain and may be defined by N^(RB) _(sc) (e.g., 12)consecutive subcarriers in the frequency domain. As a reference, aresource including one OFDM symbol and one subcarrier may be referred toas a resource element (RE) or a tone. Therefore, one RB may includeN^(slot) _(symb)*N^(RB) _(sc) resource elements. Each resource elementin the resource grid may be uniquely defined by a pair of indexes (k, l)in one slot. k may be an index numbered from 0 to N^(size, μ)_(grid, x)*N^(RB) _(sc)−1 in the frequency domain, and l may be an indexnumbered from 0 to N^(slot) _(symb)−1 in the time domain.

On the other hand, one RB may be mapped to one physical resource block(PRB) and one virtual resource block (VRB). The PRB may be defined byN^(slot) _(symb) (e.g., 14) consecutive OFDM symbols in the time domain.Further, the PRB may be defined by N^(RB) _(sc) (e.g., 12) consecutivesubcarriers in the frequency domain. Therefore, one PRB may includeN^(RB) _(sc)*N^(slot) _(symb) resource elements.

In order for the user equipment to receive a signal from the basestation or to transmit a signal to the base station, the time/frequencysynchronization of the user equipment may be synchronized with thetime/frequency synchronization of the base station. This is because thebase station and the user equipment need to be synchronized, so thatuser equipment can determine the time and frequency parameters requiredfor demodulating the DL signal and transmitting the UL signal at thecorrect time.

Each symbol of a radio frame operating in a time division duplex (TDD)or an unpaired spectrum may be configured as at least one of a DLsymbol, an UL symbol, and a flexible symbol. A radio frame operating ina DL carrier in a frequency division duplex (FDD) or a paired spectrummay be configured as a DL symbol or a flexible symbol. A radio frameoperating in an UL carrier may be configured as an UL symbol or aflexible symbol. In the DL symbol, DL transmission is possible, but ULtransmission is impossible. In the UL symbol, UL transmission ispossible, but DL transmission is impossible. The flexible symbol may bedetermined to be used as a DL or an UL according to another signal.Information on the type of each symbol, i.e., DL symbols, UL symbols,and flexible symbols, may be configured by a cell-specific or commonradio resource control (RRC) signal. In addition, information on thetype of each symbol may additionally be configured by a UE-specific ordedicated RRC signal. The base station informs, by using thecell-specific RRC signal, the number of slots with only DL symbols fromthe starting of the period of cell-specific slot configuration and theperiod of cell-specific slot configuration, the number of DL symbolsfrom the first symbol of the slot immediately following the slot withonly DL symbols, the number of slots with only UL symbols from the endof the period of cell-specific slot configuration, and the number of ULsymbols from the last symbol of the slot immediately before the slotwith only the UL symbol. Here, symbols not configured as a UL symbol anda DL symbol are flexible symbols. When information on a symbol type isconfigured by a specific-UE RRC signal, the base station may signalwhether the flexible symbol is a DL symbol or an UL symbol in acell-specific RRC signal. At this time, the specific-UE RRC signal cannot change DL symbol or UL symbol configured by the cell-specific RRCsignal into another symbol type. The specific-UE RRC signal may signalthe number of DL symbols among the N^(slot) _(symb) symbols of thecorresponding Slot for each slot, and the number of UL symbols among theN^(slot) _(symb) symbols of the slot. At this time, the DL symbol of theslot may be continuously configured from the first symbol of the slot.In addition, UL symbols of the slots may be continuously configured upto the last symbol of the slot. In this case, symbols not configured asa UL symbol and a DL symbol in a slot are flexible symbols. The type ofsymbol configured by the above RRC signal may be referred to as asemi-static DL/UL configuration. A flexible symbol of a semi-staticDL/UL configuration configured by the RRC signal may be indicated as aDL symbol, a UL symbol, or a flexible symbol by dynamic slot formatinformation (SFI). At this time, the DL symbol or UL symbol configuredby the RRC signal is not changed to another symbol type. Table 1 willillustrate the dynamic SFI that the base station may indicate to theterminal. In Table 1, D denotes a DL symbol, U denotes a UL symbol, andX denotes a flexible symbol. As shown in Table 1, up to two DL/ULswitching in one slot may be allowed.

TABLE 1 Symbol number in a slot index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 0D D D D D D D D D D D D D D 1 U U U U U U U U U U U U U U 2 X X X X X XX X X X X X X X 3 D D D D D D D D D D D D D X 4 D D D D D D D D D D D DX X 5 D D D D D D D D D D D X X X 6 D D D D D D D D D D X X X X 7 D U DD D D D D D X X X X X 8 X X X X X X X X X X X X X U 9 X X X X X X X X XX X X U U 10 X U U U U U U U U U U U U U 11 X X U U U U U U U U U U U U12 X X X U U U U U U U U U U U 13 X X X X U U U U U U U U U U 14 X X X XX U U U U U U U U U 15 X X X X X X U U U U U U U U 16 D X X X X X X X XX X X X X 17 D D X X X X X X X X X X X X 18 D D D X X X X X X X X X X X19 D X X X X X X X X X X X X U 20 D D X X X X X X X X X X X U 21 D D D XX X X X X X X X X U 22 D X X X X X X X X X X X U U 23 D D X X X X X X XX X X U U 24 D D D X X X X X X X X X U U 25 D X X X X X X X X X X U U U26 D D X X X X X X X X X U U U 27 D D D X X X X X X X X U U U 28 D D D DD D D D D D D D X U 29 D D D D D D D D D D D X X U 30 D D D D D D D D DD X X X U 31 D D D D D D D D D D D X U U 32 D D D D D D D D D D X X U U33 D D D D D D D D D X X X U U 34 D X U U U U U U U U U U U U 35 D D X UU U U U U U U U U U 36 D D D X U U U U U U U U U U 37 D X X U U U U U UU U U U U 38 D D X X U U U U U U U U U U 39 D D D X X U U U U U U U U U40 D X X X U U U U U U U U U U 41 D D X X X U U U U U U U U U 42 D D D XX X U U U U U U U U 43 D D D D D D D D D X X X X U 44 D D D D D D X X XX X X U U 45 D D D D D D X X U U U U U U 46 D D D D D X U D D D D D X U47 D D X U U U U D D X U U U U 48 D X U U U U U D X U U U U U 49 D D D DX X U D D D D X X U 50 D D X X U U U D D X X U U U 51 D X X U U U U D XX U U U U 52 D X X X X X U D X X X X X U 53 D D X X X X U D D X X X X U54 X X X X X X X D D D D D D D 55 D D X X X U U U D D D D D D 56~255Reserved

FIG. 3 is a diagram for explaining a physical channel used in a 3GPPsystem (e.g., NR) and a general signal transmission method using thephysical channel. When the power of the user equipment is turned on orthe user equipment enters a new cell, the user equipment performs aninitial cell search (S301). Specifically, the user equipment maysynchronize with the base station in the initial cell search. For this,the user equipment may receive a Primary Synchronization Signal (PSS)and a Secondary Synchronization Signal (SSS) from a base station,synchronize with the base station, and obtain information such as a cellID. Thereafter, the user equipment may receive the physical broadcastchannel from the base station and obtain the in-cell broadcastinformation. Upon completion of the initial cell search, the userequipment receives a Physical Downlink Control Channel (PDCCH) and aPhysical Downlink Shared Channel (PDSCH) according to informationcarried in the PDCCH, so that the user equipment can obtain morespecific system information than the system information obtained throughthe initial cell search (S302). When the user equipment initiallyaccesses the base station or does not have radio resources for signaltransmission, the user equipment may perform a random access procedureon the base station (S303 to S306). For this, the user equipment maytransmit a specific sequence as a preamble through a Physical RandomAccess Channel (PRACH) (S303 and S305) and receive a response messagefor the preamble on the PDCCH and the corresponding PDSCH from the basestation (S304 and S306). In case of the contention-based RACH, acontention resolution procedure may be additionally performed. After theabove-described procedure, the user equipment receives PDCCH/PDSCH(S307) and transmits a Physical Uplink Shared Channel (PUSCH)/PhysicalUplink Control Channel (PUCCH) (S308) as a general phase/DL signaltransmission procedure. In particular, the user equipment may receive DLControl Information (DCI) through the PDCCH. The DCI may include controlinformation such as resource allocation information for the userequipment. Also, the format of the DCI may vary depending on theintended use of the DCI. The control information that the user equipmenttransmits to or receives from the base station through the UL includes aDL/UL ACK/NACK signal, a Channel Quality Indicator (CQI), a PrecodingMatrix Index (PMI), a Rank Indicator (RI). In the 3GPP NR system, theuser equipment may transmit control information such as HARQ-ACK and CSIdescribed above through the PUSCH and/or PUCCH.

FIG. 4 illustrates an SS/PBCH block for initial cell access in a 3GPP NRsystem.

When the power of the user equipment is turned on and the user equipmenttries to access a new cell, the user equipment may obtain time andfrequency synchronization with the cell and perform an initial cellsearch procedure. The user equipment can detect the physical cellidentity N^(cell) _(ID) of the cell in the initial cell searchprocedure. For this, the user equipment may receive a synchronizationsignal, for example, a PSS and an SSS from a base station andsynchronize with the base station. In this case, the user equipment mayobtain information such as a cell identity (ID). Referring to FIG. 4(a),a synchronization signal will be described in more detail. Thesynchronization signal may be divided into PSS and SSS. The PSS may beused to obtain time domain synchronization and/or frequency domainsynchronization, such as OFDM symbol synchronization and slotsynchronization. The SSS may be used to obtain frame synchronization andcell group ID. Referring to FIG. 4(a) and Table 2, the SS/PBCH blockconsists of 20 RBs (=240 subcarriers) in the frequency axis, andconsists of 4 OFDM symbols in the time axis. Here, in the SS/PBCH block,PSS in the first OFDM symbol and SSS in the third OFDM symbol aretransmitted in 56, 57, . . . , 182 subcarriers. Here, the lowestsubcarrier index of the SS/PBCH block is numbered from 0. In the firstOFDM symbol in which the PSS is transmitted, the base station does nottransmit a signal in the remaining subcarriers, that is, 0, 1, . . . ,55, 183, 184, . . . , 239 subcarriers. In the third OFDM symbol in whichthe SSS is transmitted, the base station does not transmit a signal in48, 49, . . . , 55, 183, 184, . . . , 191 subcarriers. In the SS/PBCHblock, the base station transmits the PBCH signal through the remainingRE except the above signal.

TABLE 2 OFDM symbol number l Subcarrier number k Channel relative to thestart relative to the start or signal of an SS/PBCH block of an SS/PBCHblock PSS 0 56, 57, . . . , 182 SSS 2 56, 57, . . . , 182 Set 0 0, 1, .. . , 55, to 0 183, 184, . . . , 239 2 48, 49, . . . , 55, 183, 184, . .. , 191 PBCH 1, 3 0, 1, . . . , 239 2 0, 1, . . . , 47, 192, 193, . . ., 239 DM-RS 1, 3 0 + v, 4 + v, 8 + v, . . . , 236 + v for 2 0 + v, 4 +v, 8 + v, . . . , 44 + v PBCH 192 + v, 196 + v, . . . , 236 + v

The SS may represent a total of 1008 unique physical layer cell IDsthrough a combination of 3 PSSs and 336 SSs. Specifically, the physicallayer cell ID is grouped into 336 physical-layer cell-identifier groups,where each group includes 3 unique identifiers such that eachphysical-layer cell ID is part of only one physical-layercell-identifier group. Therefore, the physical layer cell identifierN^(cell) _(ID)=3N⁽¹⁾ _(ID)+N⁽²⁾ _(ID) may be defined by a number N⁽¹⁾_(ID) ranging from 0 to 335 indicating a physical-layer cell-identifiergroup and a number N⁽²⁾ _(ID) ranging from 0 to 2 indicating aphysical-layer identifier in the physical-layer cell-identifier group.The user equipment may detect the PSS and identify one of the threeunique physical-layer identifiers. In addition, the user equipment maydetect the SSS and identify one of the 336 physical layer cell IDsassociated with the physical-layer identifier. The PSS signal is asfollows.d _(PSS)(n)=1−2x(m)m=(n+43N _(ID) ⁽²⁾)mod 1270≤n<127

Here, x(i+7)=(x(i+4)+x(i))mod 2 and

[x(6)x(5)x(4)x(3)x(2)x(1)x(0)]=[1 1 1 0 1 1 0]. SSS is as follows.

d_(SSS)(n) = [1 − 2x₀((n + m₀)mod 127)][1 − 2x₁((n + m₁)mod 127)]$\mspace{20mu}{m_{0} = {{15\lfloor \frac{N_{ID}^{(1)}}{112} \rfloor} + {5N_{ID}^{(2)}}}}$  m₁ = N_(ID)⁽¹⁾mod 112   0 ≤ n < 127  x₀(i + 7) = (x₀(i + 4) + x₀(i))mod 2$\mspace{20mu}{{Here},{{x_{1}( {i + 7} )} = {{( {{x_{i}( {i + 1} )} + {x_{1}(i)}} ){mod}\; 2\mspace{14mu}{{and}\begin{bmatrix}{x_{0}(6)} & {x_{0}(5)} & {x_{0}(4)} & {x_{0}(3)} & {x_{0}(2)} & {x_{0}(1)} & {x_{0}(0)}\end{bmatrix}}} = {\quad{{\begin{bmatrix}0 & 0 & 0 & 0 & 0 & 0 & 1\end{bmatrix}\begin{bmatrix}{x_{1}(6)} & {x_{1}(5)} & {x_{1}(4)} & {x_{1}(3)} & {x_{1}(2)} & {x_{1}(1)} & {x_{1}(0)}\end{bmatrix}} = {\quad{\begin{bmatrix}0 & 0 & 0 & 0 & 0 & 0 & 1\end{bmatrix}.}}}}}}}$

A wireless frame with a 10 ms duration may be divided into two halfframes with a duration of 5 ms. Referring to FIG. 4(b), a descriptionwill be made of a slot in which SS/PBCH blocks are transmitted in eachhalf frame. A slot in which the SS/PBCH block is transmitted may be anyone of the cases A, B, C, D, and E. In the case A, the subcarrierspacing is 15 kHz and the starting time point of the SS/PBCH block is{2, 8}+14*n symbols. In this case, n=0, 1 at a carrier frequency of 3GHz or less. At frequencies below 6 GHz above 3 GHz, n=0, 1, 2, or 3. Inthe case B, the subcarrier spacing is 30 kHz and the starting time pointof the SS/PBCH block is {4, 8, 16, 20}+28*n. In this case, n=0, 1 at acarrier frequency of 3 GHz or less. At frequencies below 6 GHz above 3GHz, n=0 or 1. In the case C, the subcarrier spacing is 30 kHz and thestarting time point of the SS/PBCH block is {2, 8}+14*n. In this case,n=0 or 1 at a carrier frequency of 3 GHz or less. At frequencies below 6GHz above 3 GHz, n=0, 1, 2, or 3. In the case D, the subcarrier spacingis 120 kHz and the starting time point of the SS/PBCH block is {4, 8,16, 20}+28*n. In this case, at a carrier frequency of 6 GHz or more,n=0, 1, 2, 3, 5, 6, 7, 8, 10, 11, 12, 13, 15, 16, 17, or 18. In the caseE, the subcarrier spacing is 240 kHz and the starting time point of theSS/PBCH block is {8, 12, 16, 20, 32, 36, 40, 44}+56*n. In this case, ata carrier frequency of 6 GHz or more, n=0, 1, 2, 3, 5, 6, 7, or 8.

FIG. 5 relates to a procedure for transmission of control informationand control channel in a 3GPP NR system. Referring to FIG. 5(a), thebase station may add a cyclic redundancy check (CRC) masked with a radionetwork temporary identifier (RNTI) (e.g., an XOR operation) to controlinformation (e.g., Downlink Control Information, DCI) (S502). The basestation may scramble the CRC with an RNTI value determined according tothe purpose/target of each control information. The common RNTI used byone or more terminals may include at least one of a system informationRNTI (SI-RNTI), a paging RNTI (P-RNTI), a random access RNTI (RA-RNTI),and a transmit power control RNTI (TPC-RNTI). In addition, theUE-specific RNTI may include at least one of cell temporary RNTI(C-RNTI) and semi-persistent scheduling (SPS C-RNTI). Thereafter, thebase station may perform rate-matching according to the amount ofresource(s) used for PDCCH transmission (S506) after performing channelcoding (e.g., polar coding) (S504). Subsequently, the base station maymultiplex DCI(s) based on a control channel element (CCE) based PDCCHstructure (S508), apply additional processes (e.g., scrambling,modulation (e.g., QPSK), and interleaving) (S910) for the multiplexedDCI(s), and thereafter, map it to a resource to be transmitted. The CCEis a basic resource unit for the PDCCH, and one CCE may consist of aplurality (e.g., six) resource element groups (REGs). One REG mayconsist of a plurality of (e.g., 12) REs. The number of CCEs used forone PDCCH may be defined as an aggregation level. In 3GPP NR system, 1,2, 4, 8 or 16 can be used. FIG. 5(b) is a diagram illustrating the CCEaggregation level and the PDCCH multiplexing. In this case, the type ofthe CCE aggregation level used for one PDCCH and the CCE(s) transmittedin the control region accordingly are described.

FIG. 6 is a diagram illustrating a control resource set (CORESET) inwhich a physical downlink control channel (PDCCH) in a 3GPP NR systemmay be transmitted.

CORESET is a time-frequency resource in which PDCCH, that is, a controlsignal of a user equipment, is transmitted. Referring to FIG. 6, theuser equipment may decode the PDCCH mapped in the CORESET by receivingonly time-frequency resources defined by CORESET, instead of attemptingto decode the PDCCH by receiving all the frequency bands. The basestation may configure one or more CORESETs for each cell to the userequipment. CORESET may be configured with up to three consecutivesymbols on the time axis. In addition, CORESET may be configuredcontinuously or discontinuously in 6 PRBs units on the frequency axis.In the embodiment of FIG. 5, CORESET #1 is configured with consecutivePRBs, and CORESET #2 and CORESET #3 are configured with discontinuousPRBs. CORESET may be located in any symbol in the slot. For example,CORESET #1 in FIG. 5 starts at the first symbol of the slot, CORESET #2starts at the fifth symbol of the slot, and CORESET #9 starts at theninth symbol of the slot.

FIG. 7 is a diagram for setting a PDCCH search space in the 3GPP NRsystem. In order to transmit the PDCCH to the user equipment, eachCORESET may have at least one search space. In the present invention,the search space is all the time-frequency resource combinations(hereinafter, a set of PDCCH candidates) through which the PDCCH of theuser equipment may be transmitted. The search space may include a commonsearch space that the user equipment of the 3GPP NR must commonlyperform a search and a Terminal-specific or UE-specific search spacethat a specific user equipment must perform a search. In the commonsearch space, it is set to monitor the PDCCH that all the userequipments in the cell belonging to the same base station are commonlyset to search. Furthermore, in the UE-specific search space, each userequipment may be set to monitor the PDCCH allocated to each userequipment in different search space positions according to the userequipment. The corresponding UE-specific search space may be partiallyoverlapped with the search space of other user equipments due to thelimited control region to which the PDCCH can be allocated. Monitoringthe PDCCH includes blind decoding PDCCH candidates in the search space.The case where the blind decoding is successful may be expressed thatthe PDCCH is (successfully) detected/received. Furthermore, the casewhere the blind decoding has failed may be expressed that the PDCCH isnot successfully detected/received.

For convenience of explanation, a PDCCH scrambled with a group common(GC) RNTI (or common control RNTI, CC-RNTI) already known to transmit ULscheduling information or DL scheduling information to one or more userequipments is referred to as a (UE) group common (GC) PDCCH or a commonPDCCH. In addition, a PDCCH scrambled with a UE-specific RNTI that aspecific user equipment already knows to transmit UL schedulinginformation or DL scheduling information to one specific user equipmentis referred to as a UE-specific (US) PDCCH.

The PDCCH signals each user equipment or user equipment group of atleast one of information related to resource allocation (i.e., DL grant)of a paging channel (PCH) and a downlink-shared channel (DL-SCH),information related to resource allocation (i.e., UL grant) of UL-SCH,and HARQ information. The base station can transmit a PCH transportblock and a downlink-shared channel (DL-SCH) transmission channelthrough a PDSCH. The base station may transmit data excluding specificcontrol information or specific service data through the PDSCH. Inaddition, the user equipment may receive data excluding specific controlinformation or specific service data through the PDSCH.

The base station may include, in the PDCCH, information on to which userequipment (one or more user equipments) PDSCH data is transmitted andhow the PDSCH data is to be received and decoded by the correspondinguser equipment, and transmit the PDCCH. For example, it is assumed thata specific PDCCH is CRC masked with an RNTI called “A”, and informationon data transmitted using a radio resource (e.g., frequency location)called “B” and a DCI format called “C”, that is, transmission formatinformation (e.g., transport block size, modulation scheme, codinginformation, etc.) is transmitted through a specific subframe. In thiscase, the user equipment in the cell monitors the PDCCH using the RNTIinformation the user equipment has, and when there is more than one userequipment with an “A” RNTI, the corresponding user equipment receivesthe PDCCH and receives the PDSCH indicated by “B” and “C” through theinformation of the received PDCCH.

Table 3 shows the physical uplink control channel (PUCCH) used in thewireless communication system.

TABLE 3 PUCCH format Length in OFDM symbols Number of bits 0 1-2  ≤2 14-14 ≤2 2 1-2  >2 3 4-14 >2 4 4-14 >2

The PUCCH may be used to transmit the following control information.

-   -   Scheduling Request (SR): Information used to request a UL UL-SCH        resource.    -   HARQ-ACK: A response to the PDCCH (which indicates DL SPS        release) and/or a response to a DL data packet on the PDSCH. It        indicates whether PDCCH or PDSCH has been successfully received.        The HARQ-ACK response includes positive ACK (simply ACK),        negative ACK (hereinafter NACK), Discontinuous Transmission        (DTX), or NACK/DTX. Here, the term HARQ-ACK is interchangeably        used with HARQ ACK/NACK and ACK/NACK. In general, ACK may be        represented by 1 and NACK may be represented by 0.    -   Channel State Information (CSI): This is feedback information on        the DL channel. It is generated by the user equipment based on        the CSI-reference signal (RS) transmitted by the base station.        Multiple Input Multiple Output (MIMO)-related feedback        information includes a Rank Indicator (RI) and a Precoding        Matrix Indicator (PMI). CSI may be divided into CSI part 1 and        CSI part 2 according to the information indicated by CSI.

In the 3GPP NR system, five PUCCH formats may be used to support variousservice scenarios and various channel environments and frame structures.

PUCCH format 0 is a format may deliver 1-bit or 2-bit HARQ-ACKinformation. PUCCH format 0 may be transmitted through one OFDM symbolor two OFDM symbols on the time axis and one PRB on the frequency axis.When PUCCH format 0 is transmitted in two OFDM symbols, the samesequence to the two symbols may be transmitted through different PRBs.Through this, the user equipment can obtain a frequency diversity gain.More specifically, the user equipment may determine a value m_(cs) of acyclic shift according to M_(bit) bits UCI (M_(bit)=1 or 2), and map asequence obtained by cyclic-shifting a base sequence having a length of12 to a predetermined value m_(cs) to 12 REs of one PRB of one OFDMsymbol and transmit it. In a case where the number of cyclic shiftsusable by the user equipment is 12 and M_(bit)=1, when the userequipment transmits UCI 0 and UCI 1, the user equipment may arranges thedifference value of the two cyclic shifts to 6. In addition, whenM_(bit)=2 and the user equipment transmits UCI 00, UCI 01, UCI 11, UCI10, the user equipment can arrange the difference of four cyclic shiftvalues to 3.

PUCCH format 1 may deliver 1-bit or 2-bit HARQ-ACK information. PUCCHformat 1 may be transmitted through consecutive OFDM symbols on the timeaxis and one PRB on the frequency axis. Here, the number of OFDM symbolsoccupied by PUCCH format 1 may be one of 4, 5, 6, 7, 8, 9, 10, 11, 12,13, and 14. More specifically, M_(bit)=1 UCI may be BPSK-modulated. Theuser equipment generates a complex valued symbol d(0) by quadraturephase shift keying (QPSK) modulation of M_(bit)=2 UCI and multiplies thegenerated d(0) by a sequence of length 12 to obtain a signal. The userequipment transmits the obtained signal by spreading the even-numberedOFDM symbol to which PUCCH format 1 is allocated through the time axisorthogonal cover code (OCC). PUCCH format 1 determines the maximumnumber of different user equipments multiplexed in the same PRBaccording to the length of the OCC to be used. In the odd-numbered OFDMsymbols of PUCCH format 1, demodulation RS (DMRS) is spread with OCC andmapped.

PUCCH format 2 may deliver Uplink Control Information (UCI) exceeding 2bits. PUCCH format 2 may be transmitted through one OFDM symbol or twoOFDM symbols on the time axis and one PRB on the frequency axis. WhenPUCCH format 2 is transmitted in two OFDM symbols, the same sequence tothe two different OFDM symbols may be transmitted through differentPRBs. Through this, the user equipment can obtain a frequency diversitygain. More specifically, M_(bit) bits UCI (M_(bit)>2) is bit-levelscrambled, QPSK-modulated, and mapped to the PRB(s) of the OFDM symbol.Here, the number of PRBs may be any one of 1, 2, . . . , 16.

PUCCH format 3 or PUCCH format 4 may deliver a UCI exceeding 2 bits.PUCCH format 3 or PUCCH format 4 may be transmitted through consecutiveOFDM symbols on the time axis and one PRB on the frequency axis. Thenumber of OFDM symbols occupied by PUCCH format 3 or PUCCH format 4 maybe one of 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, and 14. Specifically, theuser equipment modulates M_(bit) bits UCI (M_(bit)>2) with π/2-binaryphase shift keying (BPSK) or QPSK to generate a complex valued symbold(0), . . . , d(Msymb−1). The user equipment may not apply block-wisespreading to PUCCH format 3. However, the user equipment may applyblock-wise spreading to one RB (12 subcarriers) using a length-12PreDFT-OCC so that PUCCH format 4 can have two or four multiplexingcapacities. The user equipment performs transmit precoding (orDFT-precoding) on the spread signal and mapping it to each RE totransmit the spread signal.

In this case, the number of PRBs occupied by PUCCH format 2, PUCCHformat 3, or PUCCH format 4 may be determined according to the lengthand maximum code rate of the UCI transmitted by the user equipment. Whenthe user equipment uses PUCCH format 2, the user equipment can transmitHARQ-ACK information and CSI information together through the PUCCH.When the number of PRBs that the user equipment can transmit is greaterthan the maximum number of PRBs that PUCCH format 2, or PUCCH format 3,or PUCCH format 4 is capable of using, the user equipment may transmitonly the remaining UCI information without transmitting some UCIinformation according to the priority of the UCI information.

PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configuredthrough the RRC signal to indicate frequency hopping in a slot. Whenfrequency hopping is configured, the index of the PRB to be frequencyhopped may be configured with the RRC signal. When PUCCH format 1, orPUCCH format 3, or PUCCH format 4 is transmitted through N OFDM symbolson the time axis, the first hop may have floor (N/2) OFDM symbols andthe second hop may have ceiling(N/2) OFDM symbols.

PUCCH format 1, PUCCH format 3, or PUCCH format 4 may be configured tobe repeatedly transmitted in a plurality of slots. In this case, thenumber K of slots in which the PUCCH is repeatedly transmitted may beconfigured by the RRC signal. The repeatedly transmitted PUCCHs isrequired to start at an OFDM symbol of the same position in each slot,and have the same length. When one OFDM symbol among OFDM symbols of aslot in which the user equipment is required to transmit a PUCCH isindicated as a DL symbol by an RRC signal, the user equipment may nottransmit the PUCCH in a corresponding slot and delay the transmission ofthe PUCCH to the next slot to transmit the PUCCH.

In the 3GPP NR system, a user equipment can performtransmission/reception using a bandwidth less than or equal to thebandwidth of a carrier (or cell). For this, the user equipment may beconfigured with a Bandwidth part (BWP) consisting of a continuousbandwidth which is a part of the bandwidth of the carrier. A userequipment operating according to TDD or operating in an unpairedspectrum may be configured with up to four DL/UL BWP pairs in onecarrier (or cell). In addition, the user equipment may activate oneDL/UL BWP pair. A user equipment operating according to FDD or operatingin paired spectrum can receive up to four DL BWPs on a DL carrier (orcell) and up to four UL BWPs on a UL carrier (or cell). The userequipment may activate one DL BWP and one UL BWP for each carrier (orcell). The user equipment may or may not perform reception ortransmission in a time-frequency resource other than the activated BWP.The activated BWP may be referred to as an active BWP.

The base station may indicate using the downlink control information(DCI) that the user equipment switch from one BWP to another BWP.Switching from one BWP to another BWP by the user equipment may indicatethat the user equipment deactivates the BWP used by the user equipmentand activates the new BWP. In a carrier (or cell) operating in TDD, thebase station may include a Bandwidth part indicator (BPI) indicating theBWP to be activated in the DCI scheduling PDSCH or PUSCH to change theDL/UL BWP pair of the user equipment. The user equipment may receive theDCI scheduling the PDSCH or PUSCH and may identify the DL/UL BWP pairactivated based on the BPI. For a DL carrier (or cell) operating as anFDD, the base station may include a BPI indicating the BWP to beactivated in the DCI scheduling PDSCH to change the DL BWP of the userequipment. For a UL carrier (or cell) operating as an FDD, the basestation may include a BPI indicating the BWP to be activated in the DCIscheduling PUSCH to change the UL BWP of the user equipment.

Hereinafter, a carrier aggregation technique will be described. FIG. 6is a conceptual diagram illustrating carrier aggregation.

Carrier aggregation is a method in which the user equipment uses aplurality of frequency blocks or cells (in the logical sense) includingUL resources (or component carriers) and/or DL resources (or componentcarriers) as one large logical frequency band in order for a wirelesscommunication system to use a wider frequency band. Hereinafter, forconvenience of description, the term “component carrier” is used.

Referring to FIG. 8, as an example of a 3GPP NR system, a total systembandwidth includes up to 16 ∂component carriers, and each componentcarrier may be capable of having a bandwidth up to 400 MHz. A componentcarrier may include one or more physically contiguous subcarriers.Although it is shown in FIG. 8 that each of the component carriers hasthe same bandwidth, this is merely an example, and each componentcarrier may have a different bandwidth. Also, although each componentcarrier is shown as being adjacent to each other in the frequency axis,the drawings are shown in a logical concept, and each component carriermay be physically adjacent to one another, or may be spaced apart.

Different center frequencies may be used for each component carrier.Also, one common center carrier may be used in a physically adjacentcomponent carrier. Assuming that all the component carriers arephysically adjacent in the embodiment of FIG. 8, the center carrier Amay be used in all the component carriers. Further, assuming that therespective component carriers are not physically adjacent to each other,the center carrier A and the center carrier B may be used in each of thecomponent carriers.

When the total system band is extended by carrier aggregation, thefrequency band used for communication with each user equipment may bedefined in units of a component carrier. The user equipment A can use100 MHz, which is the total system band, and performs communicationusing all five component carriers. The user equipments B1 to B5 can useonly 20 MHz bandwidth and perform communication using one componentcarrier. The user equipments C₁ and C₂ can use a 40 MHz bandwidth andperform communication using two component carriers, respectively. Thetwo component carriers may be logically/physically adjacent ornon-adjacent. The user equipment C₁ represents the case of using twonon-adjacent component carriers, and user equipment C₂ represents thecase of using two adjacent component carriers.

FIG. 9 is a diagram for explaining single carrier communication andmulti-carrier communication. Particularly, FIG. 7(a) shows a singlecarrier subframe structure and FIG. 7(b) shows a multi-carrier subframestructure.

Referring to FIG. 9(a), a general wireless communication system performsdata transmission or reception (in a frequency division duplex (FDD)mode) through one DL band and one UL band corresponding thereto. Inanother specific embodiment, a wireless communication system may dividea wireless frame into a UL time unit and a DL time unit in a timedomain, and perform data transmission or reception (in a time divisionduplex (TDD) mode) through the UL/DL time unit. Referring to FIG. 9(b),three 20 MHz CCs may be aggregated into UL and DL, respectively, so thata bandwidth of 60 MHz may be supported. Each CC may be adjacent ornon-adjacent to one another in the frequency domain. FIG. 9(b) shows acase where the bandwidth of the UL CC and the bandwidth of the DL CC arethe same and symmetric, but the bandwidth of each CC may be determinedindependently. In addition, asymmetric carrier aggregation withdifferent number of UL CCs and DL CCs is possible. A DL/UL CC that islimited to a specific user equipment through RRC may be referred to as aconfigured serving UL/DL CC at a specific user equipment.

The base station may be used to communicate with the user equipment byactivating some or all of the serving CCs configured in the userequipment, or by deactivating some CCs. The base station can change theCC to be activated/deactivated, and change the number of CCs to beactivated/deactivated. If the base station allocates a CC available forthe user equipment to a cell-specific or UE-specific, then at least oneof the allocated CCs is deactivated, unless the CC allocation for theuser equipment is completely reconfigured or the user equipment ishandover. One CC that is not deactivated by the user equipment is calleda Primary CC (PCC), and a CC that the base station can freelyactivate/deactivate is called a Secondary CC (SCC). PCC and SCC may bedistinguished based on control information. For example, specificcontrol information may be set to be transmitted and received onlythrough a specific CC, and this specific CC may be referred to as PCCand the remaining CC(s) may be referred to as SCC(s).

Meanwhile, 3GPP NR uses the concept of a cell to manage radio resources.A cell is defined by a combination of DL resources and UL resources,that is, a combination of DL CC and UL CC. A cell may be configured withDL resources alone, or a combination of DL resources and UL resources.If carrier aggregation is supported, the linkage between the carrierfrequency of the DL resource (or DL CC) and the carrier frequency of theUL resource (or UL CC) may be indicated by system information. In thecase of user equipments that are in the RRC_CONNECTED state but notconfigured for carrier aggregation or that do not support carrieraggregation, there is only one serving cell configured with PCell.

As mentioned above, the term “cell” used in carrier aggregation isdistinguished from the term “cell” which refers to a certaingeographical area in which a communication service is provided by onebase station or one antenna group. In order to distinguish between acell referring to a certain geographical area and a cell of carrieraggregation, in the present invention, a cell of a carrier aggregationis referred to as a CC, and a cell of a geographical area is referred toas a cell.

FIG. 10 is a diagram showing an example in which a cross carrierscheduling technique is applied. In particular, in FIG. 10, the numberof allocated cells (or component carriers) is 3, and cross carrierscheduling technique is performed using CIF as described above. Here, itis assumed that the DL cell #0 is a DL primary component carrier (i.e.,Primary Cell (PCell)), and it is assumed that the remaining componentcarriers #1 and #2 are secondary component carriers (i.e., SecondaryCell (SCell)).

The present invention proposes a method of effectively managing ULresources for a primary component carrier (primary component carrier orprimary cell or PCell) or a secondary component carrier (secondarycomponent carrier or secondary cell or SCell) during a carrieraggregation operation of the user equipment. Hereinafter, the case wherethe user equipment operates by aggregating two component carriers isdescribed, but it is obvious that the present invention can also beapplied to the case of aggregating three or more component carriers.

FIGS. 9 to 10 exemplarily illustrate a subframe structure of a 3GPPLTE-A system, but the present invention may also be applied to a 3GPP NRsystem. In the 3GPP NR system, the subframes in FIGS. 9 to 10 may bereplaced with slots.

Hereinafter, the present invention will be described. In order tofacilitate understanding of the description, each content is describedby separate embodiments, but each embodiment may be used in combinationwith each other.

FIG. 11 is a block diagram illustrating configurations of a userequipment and a base station according to an exemplary embodiment of thepresent invention.

As illustrated, the user equipment 100 according to an embodiment of thepresent invention may include a processor 110, a communication module120, a memory 130, a user interface unit 140, and a display unit 150.

First, the processor 110 may execute various commands or programs andprocess internal data of the user equipment 100. In addition, theprocessor 100 may control an overall operation including each unit ofthe user equipment 100 and control data transmission and receptionbetween the units. In this case, the processor 110 may be configured toperform an operation according to the embodiment described in thepresent invention. For example, the processor 110 may receive slotconfiguration information, determine a slot configuration based on theslot configuration information, and perform communication according tothe determined slot configuration.

Next, the communication module 120 may be an integrated module thatperforms wireless communication using a wireless communication networkand wireless LAN access using a wireless LAN. To this end, thecommunication module 120 may include a plurality of network interfacecards such as the cellular communication interface cards 121 and 122 andthe wireless LAN interface card 123 in an internal or external form.Although the communication module 120 is illustrated as an integratedmodule in the drawing, each network interface card may be independentlyarranged according to a circuit configuration or a purpose, unlike thedrawing.

The cellular communication interface card 121 may transmit and receive awireless signal with at least one of the base station 200, an externaldevice, and a server by using a mobile communication network, and mayprovide the cellular communication service thorough the first frequencyband based on a command of the processor 110. In this case, the wirelesssignal may include various types of data or information such as a voicecall signal, a video call signal, a text/multimedia message, or thelike. The cellular communication interface card 121 may include at leastone NIC module using an LTE-Licensed frequency band. The at least oneNIC module may independently perform cellular communication with atleast one of the base station 200, an external device, and a serveraccording to a cellular communication standard or protocol of afrequency band supported by the corresponding NIC module.

The cellular communication interface card 122 may transmit and receive awireless signal with at least one of the base station 200, an externaldevice, and a server by using a mobile communication network, and mayprovide the cellular communication service through the second frequencyband based on a command of the processor 110. The cellular communicationinterface card 122 may include at least one NIC module using anLTE-Unlicensed frequency band. For example, the LTE-Unlicensed frequencyband may be a band of 2.4 GHz or 5 GHz.

The wireless LAN interface card 123 transmits and receives a wirelesssignal with at least one of the base station 200, an external device,and a server through a wireless LAN connection, and provides a wirelessLAN service by the second frequency band based on a command of theprocessor 110. The wireless LAN interface card 123 may include at leastone NIC module using a wireless LAN frequency band. For example, thewireless LAN frequency band may be an Unlicensed radio band such as aband of 2.4 GHz or 5 GHz. The at least one NIC module may independentlyperform wireless communication with at least one of the base station200, an external device, and a server according to a wireless LANstandard or protocol of a frequency band supported by the correspondingNIC module.

Next, the memory 130 stores a control program used in the user equipment100 and various data according thereto. Such a control program mayinclude a predetermined program necessary for the user equipment 100 toperform wireless communication with at least one of the base station200, an external device, and a server.

Next, the user interface 140 includes various types of input/outputmeans provided in the user equipment 100. That is, the user interface140 may receive a user input using various input means, and theprocessor 110 may control the user equipment 100 based on the receiveduser input. In addition, the user interface 140 may perform an outputbased on a command of the processor 110 using various output means.

Next, the display unit 150 outputs various images on the display screen.The display unit 150 may output various display objects such as acontent executed by the processor 110 or a user interface based on acontrol command of the processor 110.

In addition, the base station 200 according to an embodiment of thepresent invention may include a processor 210, a communication module220, and a memory 230.

First, the processor 210 may execute various commands or programs andprocess internal data of the base station 200. In addition, theprocessor 210 may control an overall operation including each unit ofthe base station 200 and control data transmission and reception betweenthe units. In this case, the processor 210 may be configured to performan operation according to the embodiment described in the presentinvention. For example, the processor 210 may signal slot configurationinformation and perform communication according to the signaled slotconfiguration.

Next, the communication module 220 may be an integrated module thatperforms wireless communication using a wireless communication networkand wireless LAN access using a wireless LAN. To this end, thecommunication module 120 may include a plurality of network interfacecards such as the cellular communication interface cards 221 and 222 andthe wireless LAN interface card 223 in an internal or external form.Although the communication module 220 is illustrated as an integratedmodule in the drawing, each network interface card may be independentlyarranged according to a circuit configuration or a purpose, unlike thedrawing.

The cellular communication interface card 221 may transmit and receive awireless signal with at least one of above-described user equipment 100,an external device, and a server by using a mobile communicationnetwork, and may provide the cellular communication service thorough thefirst frequency band based on a command of the processor 210. In thiscase, the wireless signal may include various types of data orinformation such as a voice call signal, a video call signal, atext/multimedia message, or the like. The cellular communicationinterface card 221 may include at least one NIC module using anLTE-Licensed frequency band. The at least one NIC module mayindependently perform cellular communication with at least one of userequipment 100, an external device, and a server according to a cellularcommunication standard or protocol of a frequency band supported by thecorresponding NIC module.

The cellular communication interface card 222 may transmit and receive awireless signal with at least one of the user equipment 100, an externaldevice, and a server by using a mobile communication network, and mayprovide the cellular communication service through the second frequencyband based on a command of the processor 210. The cellular communicationinterface card 222 may include at least one NIC module using anLTE-Unlicensed frequency band. For example, the LTE-Unlicensed frequencyband may be a band of 2.4 GHz or 5 GHz. According to an embodiment ofthe present invention, the at least one NIC module may independentlyperform cellular communication with at least one of the user equipment100, an external device, and a server according to a cellularcommunication standard or protocol of a frequency band supported by thecorresponding NIC module.

The wireless LAN interface card 223 transmits and receives a wirelesssignal with at least one of the user equipment 100, an external device,and a server through a wireless LAN connection, and provides a wirelessLAN service by the second frequency band based on a command of theprocessor 210. The wireless LAN interface card 223 may include at leastone NIC module using a wireless LAN frequency band. For example, thewireless LAN frequency band may be an Unlicensed radio band such as aband of 2.4 GHz or 5 GHz. The at least one NIC module may independentlyperform wireless communication with at least one of the user equipment100, an external device, and a server according to a wireless LANstandard or protocol of a frequency band supported by the correspondingNIC module.

The user equipment 100 and the base station 200 illustrated in FIG. 11are block diagrams according to an embodiment of the present invention,in which blocks shown separately represent logically distinguishingelements of a device. Therefore, the elements of the above-describeddevice may be mounted in one chip or in a plurality of chips accordingto the design of the device. In addition, some components of the userequipment 100, for example, the user interface 140, the display unit150, and the like, may be selectively provided in the user equipment100. In addition, the user interface 140, the display unit 150, and thelike, may be additionally provided in the base station 200 as necessary.

In the present specification, the configuration of the UE may indicateconfiguration by the base station. In more detail, the base station mayconfigure a value of a parameter used in an operation of the UE or awireless communication system by transmitting a channel or a signal tothe UE.

FIG. 12 shows an example of CORESET according to an embodiment of thepresent invention in an NR system.

As described above, CORESET is a time-frequency resource in which PDCCH,that is, a control signal of UE, is transmitted. In addition, a searchspace may be mapped to one CORESET. Therefore, the UE may monitor thetime-frequency region designated as CORESET instead of monitoring allfrequency bands for receiving PDCCH, and decode the PDCCH mapped toCORESET.

In a specific embodiment, one CORESET may be provided for each cell. Inthis case, the UE accessing the cell may receive the PDCCH in the oneCORESET. In another specific embodiment, there may be a plurality ofCORESETs in one cell as shown in FIG. 12. In this case, the UE accessingthe cell may monitor one or more CORESETs. In more detail, a UEaccessing a cell may be configured by a base station to monitor one ormore CORESETs. In addition, a plurality of CORESETs allocated to one UEmay be configured to overlap each other in time-frequency resources.

The UE may determine a time-frequency region occupied in a current slotby CORESET allocated by the base station to the UE. However, the UE maybe incapable of determining the time-frequency region occupied in thecurrent slot by CORESET that the base station does not allocate to theUE or may be incapable of determining without an additional signaling.In addition, the UE may be incapable of determining the time-frequencyresource occupied by the PDSCH dynamically allocated in CORESET of atime slot later than the current and allocated by the base station tothe UE.

FIG. 13 shows an example of a BWP configured for a UE according to anembodiment of the present invention.

As described above, the UE may perform reception and transmissionthrough a BWP having a frequency bandwidth less than or equal to thefrequency bandwidth of the carrier (or cell). In a specific embodiment,one or more BWPs may be configured for the UE. When a plurality of BWPsare configured for the UE, frequency bands of the plurality of BWPs maynot overlap each other. Furthermore, one or more BWPs may be configuredfor the UE. When a plurality of BWPs are configured for the UE, theplurality of BWPs may include a BWP including a frequency bandoverlapping with that of another BWP of the plurality of BWPs. FIG.13(a) shows a case where frequency bands of a plurality of BWPs do notoverlap each other when a plurality of BWPs are configured for the UE.FIG. 13(b) shows a case where a plurality of BWPs are configured for aUE, and the plurality of BWPs include a BWP including a frequency bandoverlapping with another BWP of the plurality of BWPs. When a pluralityof BWPs are configured for the UE, the UE may perform transmission andreception using one BWP among the plurality of BWPs. This will bedescribed in detail with reference to FIG. 14.

FIG. 14 shows an example of BWP configured for a UE and CORESET for BWPaccording to an embodiment of the present invention.

When a plurality of BWPs are configured for the UE, each of theplurality of CORESETs for each of the plurality of BWPs may bepositioned in a time-frequency resource region occupied by thecorresponding BWP. When a plurality of BWPs are configured for the UE,at least one CORESET may be configured for the UE in each of theplurality of BWPs. When a plurality of BWPs are configured not tooverlap each other and when a plurality of BWPs are configured tooverlap each other, CORESET for each of the plurality of BWPs may be ina PRB occupied by the corresponding BWP. Also, when a plurality of BWPsare configured to overlap each other, in relation to CORESET for each ofa plurality of BWPs, a PRB occupied by CORESET corresponding to any oneBWP among the plurality of BWPs may overlap a PRB occupied by a BWPdifferent from the corresponding BWP among the plurality of BWPs.

In the embodiment of FIG. 14A, the first BWP bandwidth part #1 and thesecond BWP bandwidth part #2 are configured not to overlap each other.The first CORESET CORESET #1 corresponding to the first BWP Bandwidthpart #1 is in a PRB occupied by the first BWP Bandwidth part #1. Inaddition, the second CORESET CORESET #2 corresponding to the second BWPBandwidth part #2 is in a PRB occupied by the second BWP Bandwidth part#2. In the embodiment of FIG. 14(b), the second BWP Bandwidth part #2includes the entire frequency band indicated by the first BWP Bandwidthpart #1. The first CORESET CORESET #1 corresponding to the first BWPBandwidth part #1 is in a PRB occupied by the first BWP Bandwidth part#1. In addition, the second CORESET CORESET #2 corresponding to thesecond BWP Bandwidth part #2 is in a PRB occupied by the second BWPBandwidth part #2. In this case, the PRB occupied by the second CORESETCORESET #2 overlaps the PRB occupied by the first BWP Bandwidth part #1.

In order to implement various functions in the NR system, the basestation may use a time-frequency resource region scheduled to a UE foranother purpose and indicate to the UE that the scheduled time-frequencyresource region is used for another purpose. What the base station usesa time-frequency resource region scheduled for one UE for anotherpurpose may be referred to as a preemption. In addition, the UE to whichthe scheduled time-frequency resource is punctured may be referred to asan impacted UE. In addition, a UE receiving an allocated time-frequencyresource scheduled for another use may be referred to as a preemptingUE. A base station according to an embodiment of the present inventionmay perform a preemption operation as follows.

In more detail, the base station may transmit the multiplexed data bymultiplexing the delay-insensitive data and the delay-sensitive data forthe same UE or different UEs. The delay-insensitive data may be data forthe eMBB service described above. In addition, the delay-sensitive datamay be data for the URLLC service described above. In addition, the basestation may schedule delay-insensitive data based on a slot. In thiscase, the base station may schedule delay-sensitive data in a timeinterval unit having a duration shorter than the duration of the slot. Atime interval unit having a duration shorter than the duration of theslot may be referred to as a mini-slot. The number of OFDM symbols thatcan be allocated to one slot may vary depending on subcarrier spacing.When 15 kHz is used as the reference subcarrier spacing, one slot mayinclude 7 or 14 OFDM symbols. When 30 kHz is used as the referencesubcarrier spacing, one slot may include 14 OFDM symbols. Since theduration of the mini-slot is smaller than the slot duration as describedabove, the mini-slot may include one or more OFDM symbols which arewithin from one OFDM symbol to OFMD symbols smaller by one than thenumber of OFDM symbols included in the slot. In a specific embodiment,the base station may schedule delay-sensitive data in units of two OFDMsymbols or units of four OFDM symbols. In another specific embodiment,the base station may schedule delay-sensitive data in units of sevenOFDM symbols in consideration of the duration of the slot. This isbecause the payload size of delay-insensitive data is relatively large,and as the required delay time is longer, there is less need to bescheduled immediately. In addition, this is because the payload size ofdelay-sensitive data is relatively small, and as the required delay timeis shorter, there is great need to be scheduled immediately. In theseembodiments, in order to increase frequency efficiency and reduce delaytime, the base station may dynamically allocate time-frequency resourcesfor delay-sensitive services and time-frequency resources fordelay-insensitive services. Accordingly, the base station may performpreemption.

When the base station performs the preemption, the impacted UE thatreceives scheduling first may transmit other data by the base stationthrough the preemption to a part of the resources that the UE expect toreceive. Therefore, a resource in which the data actually transmittedfrom the base station to the impacted UE and the resources expected tobe received by the UE may be different from each other. The impacted UEmay receive and decode corrupted data due to data transmitted by thebase station through preemption. As a result, the decoding performanceof the UE may deteriorate, so that a serious degradation may occur inthe performance of the impacted UE. In order to prevent this, the basestation may signal which time-frequency resource is preempted to theimpacted UE.

The UE may decode the data that the base station intends to transmit tothe UE based on the signaling for the preemption. In more detail, the UEmay assume whether the intended data is transmitted from the basestation to the UE based on the signaling for the preemption. In thiscase, the UE may decode data received from the corresponding resourcefrom the base station based on the resource assuming transmission of theintended data from the base station to the UE and the resource assumingno transmission of the intended data to the UE. In this case, the datamay include at least one of a data channel and a control channel.

The preemption signaling method transmitted from the base station to theUE will be described in detail with reference to FIGS. 15 to 30. Inaddition, a group common PDCCH or UE specific PDCCH monitoring methodfor obtaining a preemption indicator in the UE will be described withreference to FIGS. 15 to 20.

FIG. 15 shows a method for a UE to monitor a preemption indicator basedon a BWP and a CORESET corresponding to the BWP according to anembodiment of the present invention.

The base station may use the control channel to transmit to the UE apreemption indicator that indicates which time-frequency resource ispreempted. The preemption indicator described in the specification mayrefer to a DCI format that is CRC scrambled with INT-RNTI. In addition,the control channel may be the PDCCH described above. In more detail,the control channel may be a group common PDCCH or a UE specific PDCCH.When the base station transmits a preemption indicator using the groupcommon PDCCH, the base station may scramble the group common PDCCH withthe group common RNTI. In this case, the group common RNTI may be avalue shared by a plurality of UEs monitoring the group common PDCCH.When the preemption indicator is included in the specific-UE PDCCH to betransmitted, the specific-UE PDCCH is scrambled with a specific-UE RNTI,and the specific-UE RNTI may be a unique value of the UE monitoring thecorresponding specific-UE PDCCH. In a specific embodiment, the UE mayapply preemption related information indicated by the preemptionindicator included in the group common PDCCH only to the BWPcorresponding to the CORESET in which the PDCCH is transmitted. Forexample, the UE may perform blind decoding on the group common PDCCHcorresponding to a specific BWP to obtain a preemption indicator, anddetermine whether the data channel or the control channel transmitted inthe corresponding BWP is affected by the preemption based on theobtained preemption indicator. If the UE does not need to check whetherthe data channel or control channel transmitted in a specific BWP isaffected by the preemption, the UE may not need to perform blinddecoding on the group common PDCCH for obtaining the preemptionindicator in the CORESET corresponding to the corresponding BWP. In suchembodiments, the UE can prevent power waste caused by blind decoding.

In the embodiment of FIG. 15(a), the first BWP bandwidth part #1 and thesecond BWP bandwidth part #2 are configured not to overlap each other.In the embodiment of FIG. 15(b), the second BWP Bandwidth part #2includes the entire frequency band indicated by the first BWP Bandwidthpart #1. In the embodiments of FIG. 15(a) and FIG. 15(b), the basestation may transmit a group common PDCCH including a preemptionindicator for signaling information on the preemption operationperformed in the first BWP BW part #1 in the first CORESET CORESET #1corresponding to the first BWP BW part #1. The UE may assume that groupcommon PDCCH or UE specific PDCCH including a preemption indicator forsignaling information on the preemption operation performed in the firstBWP BW part #1 is transmitted in the first CORESET CORESET #1corresponding to the first BWP BW part #1. In order to obtain apreemption indicator for signaling information on the preemptionoperation performed in the first BWP BW part #1, the UE may monitor thegroup common PDCCH or the UE specific PDCCH in the first CORESET CORESET#1. In addition, the base station may transmit a group common PDCCH orUE specific PDCCH including a preemption indicator for signalinginformation on the preemption operation performed in the second BWP BWpart #2 in the second CORESET CORESET #2 corresponding to the second BWPBW part #2. The UE may assume that group common PDCCH or UE specificPDCCH including a preemption indicator for signaling information on thepreemption operation performed in the second BWP BW part #2 istransmitted in the second CORESET CORESET #2 corresponding to the secondBWP BW part #2. In order to obtain a preemption indicator for signalinginformation on the preemption operation performed in the second BWP BWpart #2, the UE may monitor the group common PDCCH or the UE specificPDCCH in the first CORESET CORESET #2.

In the embodiment of FIG. 15, it is described that the base stationtransmits a preemption indicator in the next slot in which a preemptionoccurs. However, the time point at which the base station transmits thepreemption indicator is not limited to the next slot in which thepreemption occurs. In more detail, when a preemption occurs in the n-thslot slot # n, the base station may transmit a preemption indicator inthe n-th slot slot # n, which is the same slot after the preemptionoccurs. In addition, when a preemption occurs in the n-th slot slot # n,the base station may transmit a preemption indicator in the (n+1)-thslot slot # n+1 after the preemption occurs. After a preemption occursin the n-th slot slot # n, the base station may transmit a preemptionindicator in the (n+k)-th slot slot # n+k after the preemption occurs.In this case, k may be a natural number of 1 or more. The description ofthe time point at which the base station transmits the preemptionindicator may be equally applicable to other embodiments described laterunless otherwise specified.

FIG. 16 shows a method for a UE to monitor a preemption indicator basedon a CORESET corresponding to a BWP scheduled with a PDSCH according toan embodiment of the present invention.

The base station may transmit a control channel including a preemptionindicator for signaling information on the preemption occurring in theBWP in the CORESET corresponding to the BWP in which a data channel isscheduled. When a plurality of BWPs are configured to the UE not tooverlap each other, the UE may assume that a control channel including apreemption indicator for signaling information on preemption occurringin a BWP in which a data channel is scheduled is transmitted in aCORESET corresponding to the corresponding BWP. Therefore, when aplurality of BWPs are configured to the UE not to overlap each other,the UE may monitor a control channel in a CORESET corresponding to thecorresponding BWP to obtain a preemption indicator for signalinginformation on preemption occurring in a BWP in which a data channel isscheduled. Therefore, when a plurality of BWPs are configured to the UEnot to overlap each other, the UE may not monitor a control channel in aCORESET other than a CORESET corresponding to the corresponding BWP toobtain a preemption indicator for signaling information on preemptionoccurring in a BWP in which a data channel is scheduled. In suchembodiments, the control channel may be a group common PDCCH or UEspecific PDCCH. In addition, the data channel may be a PDSCH.

In the embodiment of FIG. 16, a first BWP Bandwidth part #1 and a secondBWP Bandwidth part #2 are configured to the UE, and the first BWPBandwidth part #1 and the second BWP Bandwidth part #2 do not overlapeach other. In the embodiment of FIG. 16(a), the PDSCH is scheduled onlyto the first BWP Bandwidth part #1 among the first BWP Bandwidth part #1and the second BWP Bandwidth part #2. In this case, the UE may assumethat the group common PDCCH or UE specific PDCCH including thepreemption indicator is transmitted only in the first CORESET CORESET #1corresponding to the first BWP Bandwidth part #1. Accordingly, in orderto obtain a preemption indicator for signaling information on thepreemption operation performed in the first BWP Bandwidth part #1, theUE may monitor the group common PDCCH or the UE specific PDCCH in thefirst CORESET CORESET #1. In addition, the UE may assume that a groupcommon PDCCH or UE specific PDCCH including a preemption indicator forsignaling information on the preemption operation performed in the firstBWP Bandwidth part #1 is not transmitted in a second CORESET CORESET #2not scheduled with the PDSCH. Therefore, even if the UE is configured tomonitor the second CORESET CORESET #2, the UE may not performgroup-common PDCCH or UE specific PDCCH monitoring in the second CORESETCORESET #2 to obtain a preemption indicator for signaling information onthe preemption operation performed in the first BWP Bandwidth part #1.

In the embodiment of FIG. 16(b), the PDSCH is scheduled only in thesecond BWP Bandwidth part #2 among the first BWP Bandwidth part #1 andthe second BWP Bandwidth part #2. In this case, the UE may assume thatthe group common PDCCH or UE specific PDCCH including the preemptionindicator is transmitted only in the second CORESET CORESET #2corresponding to the second BWP Bandwidth part #2. Accordingly, in orderto obtain a preemption indicator for signaling information on thepreemption operation performed in the second BWP Bandwidth part #2, theUE may monitor the group common PDCCH or the UE specific PDCCH in thesecond CORESET CORESET #2. In addition, the UE may assume that a groupcommon PDCCH or UE specific PDCCH including a preemption indicator forsignaling information on the preemption operation performed in thesecond BWP Bandwidth part #2 is not transmitted in a first CORESETCORESET #1 not scheduled with the PDSCH. Therefore, even if the UE isconfigured to monitor the first CORESET CORESET #1, the UE may notperform group-common PDCCH or UE specific PDCCH monitoring in the firstCORESET CORESET #1 to obtain a preemption indicator for signalinginformation on the preemption operation performed in the second BWPBandwidth part #2.

In the embodiment of FIG. 16(c), the PDSCH is scheduled in each of thefirst BWP Bandwidth part #1 and the second BWP Bandwidth part #2. Inthis case, the UE may assume that the group common PDCCH or UE specificPDCCH including the preemption indicator is transmitted only in thefirst CORESET CORESET #1 corresponding to the first BWP Bandwidth part#1. Accordingly, in order to obtain a preemption indicator for signalinginformation on the preemption operation performed in the first BWPBandwidth part #1, the UE may monitor the group common PDCCH or the UEspecific PDCCH in the first CORESET CORESET #1. In addition, the UE mayassume that the group common PDCCH or UE specific PDCCH including thepreemption indicator is transmitted only in the second CORESET CORESET#2 corresponding to the second BWP Bandwidth part #2. Accordingly, inorder to obtain a preemption indicator for signaling information on thepreemption operation performed in the second BWP Bandwidth part #2, theUE may monitor the group common PDCCH or the UE specific PDCCH in thesecond CORESET CORESET #2.

When a plurality of BWPs are configured to the UE to overlap each other,it may be difficult for the UE to determine which BWP is the BWPscheduled with the PDSCH. Accordingly, when a plurality of BWPs areconfigured to UE to overlap each other, a method of determining aCORESET to monitor to obtain a preemption indicator is needed. This willbe described with reference to FIG. 17.

FIG. 17 shows a method of monitoring a preemption indicator based on aCORESET corresponding to a BWP scheduled with a PDSCH when a pluralityof BWPs configured for a UE overlap each other according to anembodiment of the present invention.

When a plurality of BWPs configured to the UE to overlap each other, thebase station may transmit a control channel including a preemptionindicator for signaling information on the preemption occurring in thetransmission of the corresponding data channel in the CORESETcorresponding to the smallest BWP among the BWPs including all frequencyregions in which a data channel is scheduled. When a plurality of BWPsconfigured to the UE to overlap each other, the UE may assume that acontrol channel including a preemption indicator for signalinginformation on the preemption occurring in the transmission of thecorresponding data channel is transmitted in the CORESET correspondingto the smallest BWP among the BWPs including all frequency regions inwhich a data channel is scheduled. Therefore, when a plurality of BWPsconfigured to the UE to overlap each other, the UE may monitor a controlchannel in the CORESET corresponding to the smallest BWP among the BWPsincluding all frequency regions in which a data channel is scheduled toobtain a preemption indicator for signaling information on thepreemption occurring in the transmission of the corresponding datachannel. In addition, when a plurality of BWPs configured to the UE tooverlap each other, the UE may not monitor a control channel in aCORESET other than the CORESET corresponding to the smallest BWP amongthe BWPs including all frequency regions in which a data channel isscheduled to obtain a preemption indicator for signaling information onthe preemption occurring in the transmission of the corresponding datachannel. In such embodiments, the control channel may be a group commonPDCCH or UE specific PDCCH. In addition, in such embodiment, the datachannel may be a PDSCH.

In the embodiment of FIG. 17, the first BWP Bandwidth part #1 and thesecond BWP Bandwidth part #2 are configured for the UE. Furthermore, thesecond BWP Bandwidth part #2 includes the first BWP Bandwidth part #1.For convenience of description, in relation to the embodiment of FIG.17, a preemption indicator signaling information on preemption for PDSCHtransmission is described as a preemption indicator. In the embodimentof FIG. 17(a), the PDSCH is scheduled in a frequency region included inboth the first BWP Bandwidth part #1 and the second BWP Bandwidth part#2. Since the first BWP Bandwidth part #1 is the smallest among the BWPsincluding all frequency regions in which a PDSCH is scheduled, the UEmay assume that a group common PDCCH or UE specific PDCCH including apreemption indicator is transmitted only in the first CORESET CORESET #1corresponding to the first BWP Bandwidth part #1. Accordingly, in orderto obtain the preemption indicator, the UE may monitor the group commonPDCCH or the UE specific PDCCH in the first CORESET CORESET #1. Inaddition, the UE may assume that a group common PDCCH or UE specificPDCCH including a preemption indicator is not transmitted in the secondCORESET CORESET #2 in which the PDSCH is not scheduled. Therefore, evenif the UE is configured to monitor the second CORESET CORESET #2, the UEmay not monitor group-common PDCCH or UE specific PDCCH in the secondCORESET CORESET #2 to obtain a preemption indicator.

In the embodiment of FIG. 17(b), the PDSCH is scheduled only to thefrequency region included in the second BWP Bandwidth part #2 among thefirst BWP Bandwidth part #1 and the second BWP Bandwidth part #2. Sincethe second BWP Bandwidth part #2 is the smallest among the BWPsincluding all frequency regions in which a PDSCH is scheduled, the UEmay assume that a group common PDCCH or UE specific PDCCH including apreemption indicator is transmitted only in the second CORESET CORESET#2 corresponding to the second BWP Bandwidth part #2. Accordingly, inorder to obtain the preemption indicator, the UE may monitor the groupcommon PDCCH or the UE specific PDCCH in the second CORESET CORESET #2.In addition, the UE may assume that a group common PDCCH or UE specificPDCCH including a preemption indicator is not transmitted in the firstCORESET CORESET #1 in which the PDSCH is not scheduled. Therefore, evenif the UE is configured to monitor the first CORESET CORESET #1, the UEmay not monitor group-common PDCCH or UE specific PDCCH in the firstCORESET CORESET #1 to obtain a preemption indicator.

In the embodiment of FIG. 17(c), the first BWP Bandwidth part #1includes a part of the frequency region in which the PDSCH is scheduled,and the second BWP bandwidth part #2 includes all frequency regions thePDSCH is scheduled. Since the first BWP Bandwidth part #1 does notinclude all frequency regions in which a PDSCH is scheduled and thesecond BWP bandwidth part #2 includes all frequency regions in which aPDSCH is scheduled, the UE may assume that a group common PDCCH or UEspecific PDCCH including a preemption indicator is transmitted only inthe second CORESET CORESET #2 corresponding to the second BWP Bandwidthpart #2. Accordingly, in order to obtain the preemption indicator, theUE may monitor the group common PDCCH or the UE specific PDCCH in thesecond CORESET CORESET #2. In addition, the UE may assume that a groupcommon PDCCH or UE specific PDCCH including a preemption indicator isnot transmitted in the first CORESET CORESET #1 not scheduled with thePDSCH. Therefore, even if the UE is configured to monitor the firstCORESET CORESET #1, the UE may not monitor group-common PDCCH or UEspecific PDCCH in the first CORESET CORESET #1 to obtain a preemptionindicator.

The base station may transmit the preemption indicator using a specificUE PDCCH or a group common PDCCH. In this case, the base station maytransmit a specific UE PDCCH or a group common PDCCH including apreemption indicator through a predetermined BWP regardless of the BWPin which the PDSCH is scheduled. This will be described with referenceto FIGS. 18 to 19.

FIGS. 18 and 19 show a method in which a UE monitors a preemptionindicator based on a predetermined BWP according to an embodiment of thepresent invention.

As described above, the base station may transmit a specific UE PDCCH ora group common PDCCH including a preemption indicator through apredetermined BWP regardless of the BWP in which the PDSCH is scheduled.Therefore, it may be assumed that the UE receives a specific UE PDCCH orgroup common PDCCH including a preemption indicator through apredetermined BWP. The UE may monitor a specific UE PDCCH or groupcommon PDCCH including the preemption indicator in a predetermined BWPto obtain the preemption indicator.

In the embodiment of FIG. 18, a first BWP Bandwidth part #1 and a secondBWP Bandwidth part #2 are configured to the UE, and the first BWPBandwidth part #1 and the second BWP Bandwidth part #2 do not overlapeach other. In the embodiment of FIG. 18(a), the PDSCH is scheduled onlyin the first BWP Bandwidth part #1 among the first BWP Bandwidth part #1and the second BWP Bandwidth part #2. In the embodiment of FIG. 18(b),the PDSCH is scheduled only in the second BWP Bandwidth part #2 amongthe first BWP Bandwidth part #1 and the second BWP Bandwidth part #2. Inthe embodiment of FIG. 18(c), the PDSCH is scheduled in each of thefirst BWP Bandwidth part #1 and the second BWP Bandwidth part #2.

In the embodiment of FIG. 19, the first BWP Bandwidth part #1 and thesecond BWP Bandwidth part #2 are configured for the UE. Furthermore, thesecond BWP Bandwidth part #2 includes the first BWP Bandwidth part #1.In the embodiment of FIG. 19(a), the PDSCH is scheduled in a frequencyregion included in both the first BWP Bandwidth part #1 and the secondBWP Bandwidth part #2. In the embodiment of FIG. 19(b), the PDSCH isscheduled only in the frequency region included in the second BWPBandwidth part #2 among the first BWP Bandwidth part #1 and the secondBWP Bandwidth part #2. In the embodiment of FIG. 19(c), the first BWPBandwidth part #1 includes a part of the frequency region in which thePDSCH is scheduled, and the second BWP bandwidth part #2 includes allfrequency regions the PDSCH is scheduled.

For convenience of description, in relation to the embodiment of FIGS.18 to 19, a preemption indicator for signaling information on preemptionfor PDSCH transmission is described as a preemption indicator. In theembodiments of FIGS. 18 to 19, the base station transmits a specific UEPDCCH or group common PDCCH including the preemption indicator only in afirst CORESET CORESET #1 corresponding to a first predetermined BWPBandwidth part #1. Accordingly, the UE may assume that the specific UEPDCCH or group common PDCCH including the preemption indicator istransmitted only in the first CORESET CORESET #1 corresponding to thefirst BWP Bandwidth part #1. In order to obtain the preemptionindicator, the UE may monitor the specific UE PDCCH or group commonPDCCH in the first CORESET CORESET #1. Furthermore, in order to obtainthe preemption indicator, the UE may not monitor the specific UE PDCCHor group common PDCCH in the second CORESET CORESET #2.

The DCI payload of a specific UE PDCCH or group common PDCCH may includea preemption indicator. In this case, the length of the DCI payload ofthe specific UE PDCCH or group common PDCCH may vary. Accordingly, theUE may determine the length of the DCI payload of the specific UE PDCCHor group common PDCCH, and perform blind decoding on the specific UEPDCCH or the group common PDCCH based on the determined length of theDCI payload of the specific UE PDCCH or the group common PDCCH.

In a specific embodiment, the length of the DCI payload of a specific UEPDCCH or group common PDCCH including a preemption indicator may varydepending on the number of BWPs in which the PDSCH is transmitted. Forexample, the length of the DCI payload of the PDCCH when the frequencyregion in which the PDSCH is transmitted is included in n BWPs may belonger than the length of the DCI payload of the PDCCH when included ink BWPs. In this case, both n and k are natural numbers, and n is largerthan k. In more detail, the length of the DCI payload of the PDCCH whenthe frequency region in which the PDSCH is transmitted is included intwo BWPs may be longer than the length of the DCI payload of the PDCCHwhen the PDSCH is included in one BWP. The base station may configurethe length of the DCI payload of the PDCCH, including the preemptionindicator based on the number of BWPs in which the PDSCH is transmittedaccording to these embodiments. In addition, the UE may determine thelength of the DCI payload of the PDCCH, including the preemptionindicator based on the number of BWPs in which the PDSCH is transmittedaccording to these embodiments.

In another specific embodiment, the length of the DCI payload of aspecific UE PDCCH or group common PDCCH including a preemption indicatormay vary depending on the number of PRBs occupied by the PDSCH.Specifically, when X is the number of PRBs occupied by the PDSCH, thelength of the DCI payload of the PDCCH may increase or decrease inproportion to X. In more detail, the length of the DCI payload of thePDCCH including the preemption indicator may be ceil(k*X) bits. In thiscase, k is a number between 0 and 1, and ceil(a) is the smallest naturalnumber among integers greater than or equal to a. Unless otherwisespecified in the present specification, ceil(a) represents the smallestnatural number equal to or greater than a. The base station mayconfigure the length of the DCI payload of the PDCCH, including thepreemption indicator based on the number of BWPs occupied by the PDSCHaccording to these embodiments. In addition, the UE may determine thelength of the DCI payload of the PDCCH, including the preemptionindicator based on the number of BWPs occupied by the PDSCH according tothese embodiments.

According to another specific embodiment of the present invention, thebase station may transmit a control channel including a preemptionindicator based on a CORESET in which a control channel scheduling adata channel is transmitted. This will be described in more detail withreference to FIG. 20.

FIG. 20 shows a method for a UE to monitor a preemption indicator in aCORESET in which a PDCCH scheduling a PDSCH is transmitted according toan embodiment of the present invention.

In a specific embodiment, the base station may transmit a controlchannel including a preemption indicator for signaling information onthe preemption occurring in the transmission of the data channel in aCORESET in which control channel scheduling the corresponding datachannel is transmitted. The UE may assume the control channel includinga preemption indicator for signaling information on the preemptionoccurring in the transmission of the data channel that the data channelis transmitted in the CORESET in which the control channel schedulingthe data channel is transmitted. Therefore, in order to obtain apreemption indicator signaling information on the preemption occurringin the transmission of the data channel, the UE may monitor the controlchannel in a CORESET in which a control channel for scheduling the datachannel is transmitted in the frequency region in which the data channelis scheduled. In addition, in order to obtain a preemption indicator forsignaling information on the preemption occurring in the transmission ofthe data channel, the UE may not monitor the control channel in aCORESET other than a CORESET in which a control channel for schedulingthe data channel is transmitted in the frequency region in which thedata channel is scheduled. In such embodiments, the control channel maybe a group common PDCCH or UE specific PDCCH. In addition, in suchembodiment, the data channel may be a PDSCH.

In the embodiment of FIG. 20, the first BWP Bandwidth part #1 and thesecond BWP Bandwidth part #2 are configured for the UE. Furthermore, thesecond BWP Bandwidth part #2 includes the first BWP Bandwidth part #1.In the embodiment of FIG. 20(a), the PDSCH is scheduled in a frequencydomain included in both the first BWP Bandwidth part #1 and the secondBWP Bandwidth part #2. In the embodiment of FIG. 20(b), the PDSCH isscheduled only in the frequency region included in the second BWPBandwidth part #2 among the first BWP Bandwidth part #1 and the secondBWP Bandwidth part #2. In the embodiment of FIG. 20(c), the first BWPBandwidth part #1 includes a part of the frequency region in which thePDSCH is scheduled, and the second BWP bandwidth part #2 includes allfrequency regions in which the PDSCH is scheduled.

For convenience of description, in relation to the embodiment of FIG.20, a preemption indicator for signaling information on a preemption forPDSCH transmission is described as a preemption indicator. In theembodiments of FIGS. 20(a) to 20(c), all PDCCHs scheduling the PDSCH aretransmitted in the first CORESET CORESET #1. Accordingly, the basestation may transmit a specific UE PDCCH or group common PDCCH includingthe preemption indicator only in the first CORESET CORESET #1corresponding to the first BWP Bandwidth part #1. Accordingly, the UEmay assume that the specific UE PDCCH or group common PDCCH includingthe preemption indicator is transmitted only in a first CORESET CORESET#1 corresponding to a first BWP Bandwidth part #1. In order to obtainthe preemption indicator, the UE may monitor the specific UE PDCCH orgroup common PDCCH in the first CORESET CORESET #1. Furthermore, inorder to obtain the preemption indicator, the UE may not monitor thespecific UE PDCCH or group common PDCCH in the second CORESET CORESET#2.

A preemption indication method of the preemption indicator will bedescribed in detail with reference to FIGS. 21 to 30. In order todescribe an OFDM symbol indicating whether a preemption indicator isgenerated or not, first, a configuration of OFDM symbols included in aslot will be described.

FIG. 21 shows an example of a configuration of OFDM symbols included ina slot when TDD is used in a wireless system according to an embodimentof the present invention.

When TDD is used in a wireless system according to an embodiment of thepresent invention, a symbol included in a slot may be classified into aDL symbol, an UL symbol, and a flexible symbol. The DL symbol is asymbol for scheduling DL transmission. In addition, the UL symbol is asymbol for scheduling the UL transmission. The flexible symbol is asymbol that does not correspond to the DL symbol and the UL symbol. Theflexible symbol may be referred to as an unknown symbol. In addition,the flexible symbol may be used for the time gap required for switchingbetween DL transmission and UL transmission. The slot can have varioussymbol configurations. FIG. 21 shows an example of a symbolconfiguration included in one slot. In the embodiment of FIG. 21, oneslot includes 14 symbols. Furthermore, in the drawing, N_(DL) representsthe number of DL symbols, N_(FL) represents the number of flexiblesymbols, and N_(UL) represents the number of UL symbols. In theembodiment of FIG. 21, one slot includes seven DL symbols, threeflexible symbols, and four UL symbols.

The base station may signal the slot format to the UE using the RRCconfiguration. In this case, the base station may use at least one of acell-specific RRC signal and a UE-specific RRC signal. In more detail,the base station may signal whether each symbol of the slot correspondsto one of a DL symbol, a UL symbol, and a flexible symbol using an RRCconfiguration. In more detail, the base station may explicitly signal asymbol corresponding to a DL symbol and a symbol corresponding to a ULsymbol among a plurality of OFDM symbols included in a slot by using anRRC configuration. In a specific embodiment, the UE may determine asymbol indicated as the DL slot and the DL symbol by the cell-specificRRC signal as a DL symbol, determine a symbol indicated as the UL slotand the UL symbol by the cell-specific RRC signal as the UL symbol, anddetermine a symbol indicated as the flexible symbol by the cell-specificRRC signal as the flexible symbol. Alternatively, the UE may determine asymbol not indicated as the DL slot and the DL symbol and not indicatedas the UL slot and the UL symbol, by the cell-specific RRC signal, asthe flexible symbol.

In addition, the base station may implicitly signal that the remainingsymbols excluding the symbols corresponding to the DL symbols and thesymbols corresponding to the UL symbols among the plurality of OFDMsymbols included in the slot corresponding to the flexible symbols.Accordingly, the UE may determine a symbol included in the slot as oneof a DL symbol, a UL symbol, and a flexible symbol based on the RRCconfiguration. In more detail, the UE may determine a symbol indicatedas the DL symbol by the RRC configuration as the DL symbol and a symbolindicated as the UL symbol by the RRC configuration as the UL symbol. Inaddition, the UE may determine a symbol not indicated as a DL symbol andalso not indicated as a UL symbol, by the RRC configuration, as aflexible symbol. In a specific embodiment, the UE may determine a symbolindicated as the DL symbol by the cell-specific RRC signal as a DLsymbol, determine a symbol indicated as the UL symbol by thecell-specific RRC signal as the UL symbol, and determine a symbol notindicated as the DL symbol and the UL symbol by the cell-specific RRCsignal as the flexible symbol. In this case, the base station mayconfigure the flexible symbol by using a UE-specific RRC signal.Accordingly, the UE may determine whether the OFDM symbol indicated asthe flexible symbol by the cell-specific RRC signal is a DL symbol, a ULsymbol, or a flexible symbol based on the UE-specific RRC signal. Inmore detail, when an OFDM symbol indicated by the cell-specific RRCsignal as a flexible symbol is indicated by the UE-specific RRC signalas a DL symbol, the UE may determine the corresponding OFDM symbol as aDL symbol. In addition, when an OFDM symbol indicated by thecell-specific RRC signal as a flexible symbol is indicated by theUE-specific RRC signal as a UL symbol, the UE may determine thecorresponding OFDM symbol as a UL symbol. In addition, when an OFDMsymbol indicated by the cell-specific RRC signal as a flexible symbol isnot indicated as a UL symbol or a DL symbol, the UE may determine thecorresponding OFDM symbol as a flexible symbol. In another specificembodiment, when an OFDM symbol indicated by the cell-specific RRCsignal as a flexible symbol is indicated by the UE-specific RRC signalas a flexible symbol, the UE may determine the corresponding OFDM symbolas a flexible symbol.

The UE may always assume a symbol configured as a DL symbol by the RRCconfiguration as a DL symbol. In addition, the UE may always assume asymbol configured as a UL symbol by the RRC configuration as a ULsymbol. As mentioned above, the flexible symbol may be referred to as anunknown symbol. This is because the base station may further indicateinformation for which the flexible symbol is used through additionalsignaling. In more detail, the base station may indicate the flexiblesymbol as a DL symbol or a UL symbol through additional signaling otherthan the RRC configuration. The additional signaling other than the RRCconfiguration may include at least one of control information, controlsignal, and control channel. The control channel may include a PDCCH. Inthis case, the PDCCH may include a group common PDCCH indicatinginformation to a plurality of UEs. In addition, the PDCCH may include aspecific UE PDCCH indicating information to any one UE. The controlinformation may include a DCI. For example, the additional signalingother than RRC may be a UE-specific DCI that includes PDSCH or PUSCHscheduling information. In addition, the additional signaling other thanthe RRC may be a dynamic SFI of the L-signal indicating information onthe slot configuration. In this case, the dynamic SFI may be transmittedthrough a group-common PDCCH, and the dynamic SFI may use a DCI formathaving a CRC scrambled by the SFI-RNTI.

In addition, when the flexible symbol is not indicated as a DL symbol ora UL symbol in additional signaling other than the RRC configuration,the UE may not assume the transmission to the base station or thereception from the base station in the flexible symbol. When additionalsignaling other than the RRC configuration indicates a flexible symbolas a DL symbol or a UL symbol, the UE may assume the flexible symbol asa DL symbol or an UL symbol according to the indication of theadditional signaling. Therefore, when additional signaling indicatesthat the flexible symbol is a DL symbol, the UE may assume receptionfrom the base station in the corresponding symbol. In addition, when theadditional signaling indicates that the flexible symbol is an UL symbol,the UE may perform transmission to the base station in the correspondingsymbol.

In addition, unless otherwise specified in this specification, the RRCsignal for slot configuration may indicate the cell-specific RRC signalas system information. In relation to the base station, the name of thecell-specific RRC signal may be Slot-assignmentSIB1. In addition, thename of a UE-specific RRC signal may be Slot-assignment.

FIG. 22 shows an OFDM symbol indicated by a preemption indicatoraccording to an embodiment of the present invention.

The preemption indicator may indicate information on preemption of aplurality of OFDM symbols. For convenience of description, the OFDMsymbol indicated by the preemption indicator is referred to as areference DL resource. In addition, the base station may transmit acontrol channel including the preemption indicator every one or moreslots. The UE may monitor the control channel including the preemptionindicator every one or more slots. In this case, the UE may determine aperiod of CORESET for monitoring the preemption indicator based on theRRC signal. The duration of the reference DL resource may be determinedaccording to a period in which the base station transmits a controlchannel including the preemption indicator. In addition, the duration ofthe reference DL resource may be determined according to the period inwhich the UE monitors the control channel including the preemptionindicator.

When the UE monitors a control channel including the preemptionindicator every x slots, the preemption indicator obtained from thecontrol channel transmitted from the n-th slot may indicate informationon preemption occurring in the (n−x)-th slot, the (n−x+1)-th slot, . . ., (n−1)-th slot. Therefore, when the UE obtains the preemption indicatorfrom the control channel transmitted in the n-th slot, the UE maydetermine a preemption occurring in the (n−x)-th slot, the (n−x+1)-thslot, . . . , (n−1)-th slot based on the obtained preemption indicator.The time interval corresponding to the reference DL resource may be fromthe next symbol of the CORESET in which the control channel includingthe preemption indicator is received immediately before thecorresponding preemption indicator to the last symbol of the CORESET inwhich the control channel including the corresponding preemptionindicator is received. Alternatively, the time interval corresponding tothe reference DL resource may indicate symbols from the start symbol ofthe CORESET configured for monitoring the control channel including thepreemption indicator immediately before the received preemptionindicator to the first symbol of the CORESET in which the controlchannel including the corresponding preemption indicator is received.

The frequency band corresponding to the reference DL resource may be theentire frequency band of the BWP in which a preemption indicationindicating a preemption occurring in the reference DL resource istransmitted. In another specific embodiment, the frequency bandcorresponding to the reference DL resource may be a specific frequencyband indicated by the RRC configuration of the base station. In thiscase, the specific frequency band may be a continuous frequency band.According to a specific embodiment, the specific frequency band may be adiscontinuous frequency band.

In addition, the preemption indicator may indicate a resource preempted(or punctured) in the time domain and the frequency domain. In thiscase, the preemption indicator may include information indicating aresource preempted (or punctured) in the frequency domain.

In the embodiment of FIG. 22, the base station transmits a controlchannel including a preemption indicator every four slots. In addition,the UE monitors the control channel including the preemption indicatorevery four slots. Therefore, when a control channel including apreemption indicator is transmitted in the n-th slot, the preemptionindicator indicates which DL resource among the DL resources included inthe reference DL resource the preemption occurs from the (n−4)-th slotto the (n−1)-th slot.

As described above, the preemption indicator indicates information onwhich resource among the DL resources allocated to a specific UE ispreempted. Accordingly, the preemption indicator includes informationnecessary for the UE to which the DL resource is allocated. In addition,in relation to the preemption indicator, the UE receiving an allocatedUL resource does not need to monitor the preemption indicator. Thepreemption indicator may indicate information on the remaining OFDMsymbols except some of the OFDM symbols included in the slotcorresponding to the preemption indicator. This will be described withreference to FIGS. 23 to 26.

FIG. 23 shows an OFDM symbol indicated by a preemption indicatoraccording to an embodiment of the present invention.

Some symbols may be determined by an RRC signal indicating the use ofthe corresponding symbol. In more detail, the preemption indicator mayindicate only information on a resource corresponding to a DL symbol ora flexible symbol that may be a DL symbol. In such an embodiment, thereference DL resource may be discontinuous. The UE may determine an OFDMsymbol indicated by the information on the preemption in the preemptionindicator according to the following embodiments.

In a specific embodiment, the base station may explicitly indicate thereference DL resource corresponding to the preemption indicator usingthe RRC configuration. The UE may assume that preemption only occurs inan OFDM symbol indicated by the RRC configuration as a DL slot and a DLsymbol. In addition, the UE may assume that the preemption indicatorindicates information on preemption occurring in an OFDM symbolindicated by a reference DL resource corresponding to the preemptionindicator. For example, the base station may transmit a bitmapindicating an OFDM symbol corresponding to the reference DL resource tothe UE using the RRC signal. In this case, each bit of the bitmap mayindicate whether an OFDM symbol corresponding to each bit corresponds toa preemption indicator. In the embodiment of FIG. 23, the base stationmay transmit a control channel including a preemption indicator everyfour slots. In this case, each slot includes 14 OFDM symbols. The basestation may indicate an OFDM symbol corresponding to the reference DLresource by transmitting a bitmap having a length of 56 bits using theRRC signal. The UE may determine an OFDM symbol corresponding to thereference DL resource by obtaining a bitmap from the RRC signal.

In another specific embodiment, the UE may determine an OFDM symbolcorresponding to the reference DL resource based on the slot formatconfigured in the RRC signal. In more detail, the UE may determine thatthe OFDM symbol configured as the UL symbol by the RRC configuration isnot included in the reference DL resource. This is because the UE canalways assume an OFDM symbol configured as an UL symbol by an RRCconfiguration as a UL symbol. The UE may assume that the base stationdoes not preempt the OFDM symbol configured as the UL symbol by the RRCconfiguration. In a specific embodiment, the UE may determine that thereference DL resource includes only a symbol indicated as a DL symbol ora flexible symbol in the RRC configuration. In more detail, the basestation may configure, as reference DL resources, the remaining OFDMsymbols except for the OFDM symbols configured as the UL symbols by theRRC signal among the OFDM symbols in the preemption indicatortransmission period. In this case, the base station may configure thepreemption indicator based on the information on the preemption for thereference DL resource and signal the preemption indicator to the UEthrough the control channel. In addition, the UE may determine that theOFDM symbol configured as the UL symbol by the RRC signal is notincluded in the reference DL resource. The UE may determine, as areference DL resource, an OFDM symbol configured as a DL symbol by anRRC signal and a symbol configured as a flexible symbol by an RRC signalamong OFDM symbols between preemption indicator monitoring periods. Forexample, it is assumed that a plurality of OFDM symbols betweenpreemption indicator monitoring periods are A DL symbols configured bythe RRC signal, C flexible symbols configured by the RRC signal, and BUL symbols configured by the RRC signal. In this case, the UE maydetermine the A DL symbols configured by the RRC signal and the Cflexible symbols configured by the cell-specific signal as reference DLresources.

In such embodiments, the RRC signal may include a cell-specific RRCsignal and may not include a UE-specific RRC signal. In more detail, thebase station may configure the remaining OFDM symbols except for theOFDM symbols configured as the UL symbols by the RRC signal among theOFDM symbols in the preemption indicator transmission period asreference DL resources such that the preemption indicator may beconfigured based on the information on the preemption for the referenceDL resource. In this case, the base station may signal the preemptionindicator to the UE through the control channel. In addition, the UE maydetermine that the OFDM symbol configured as the UL symbol by thecell-specific RRC signal is not included in the reference DL resource.The UE may determine, as a reference DL resource, an OFDM symbolconfigured as a DL symbol by a cell-specific RRC signal and a symbolconfigured as a flexible symbol by a cell-specific RRC signal among OFDMsymbols between preemption indicator monitoring periods. For example, itis assumed that a plurality of OFDM symbols between preemption indicatormonitoring periods are A DL symbols configured by the cell-specific RRCsignal, C flexible symbols configured by the cell-specific RRC signal,and B UL symbols configured by the cell-specific RRC signal. In thiscase, the UE may determine the A DL symbols configured by thecell-specific RRC signal and the C flexible symbols configured by thecell-specific signal as reference DL resources.

In such embodiments, the RRC signal may include a UE-specific RRC signalas well as a cell-specific RRC signal. Accordingly, the UE may determinethat the OFDM symbol configured as the UL symbol by the cell-specificRRC signal and the OFDM symbol configured as the UL symbol by theUE-specific RRC signal are not included in the reference DL resource.The UE may determine, as a reference DL resource, the remaining symbolsexcept for an OFDM symbol configured as a DL symbol by the cell-specificRRC signal and an OFDM symbol configured as a DL symbol by the UEspecific RRC signal among OFDM symbols between preemption indicatormonitoring periods. When the UE does not receive the UE-specific RRCsignal, or if the corresponding UE-specific RRC signal is not configuredfor the UE, the UE may determine the reference DL resource based only onthe cell-specific RRC signal.

In addition, the UE may configure, as the reference DL resource, an OFDMsymbol configured as a UL symbol by an RRC signal among OFDM symbolswithin a preemption indicator transmission period and the remaining OFDMsymbols except for the n flexible symbols continuously locatedimmediately before the OFDM symbols configured as a UL symbol by the RRCsignal to exclude n flexible symbols continuously located before the ULsymbol as the reference DL resource. In more detail, the base stationmay configure the preemption indicator based on information on thepreemption for the corresponding reference DL resource by. In this case,the base station may signal the preemption indicator to the UE throughthe control channel. This is because a time gap for switching between DLtransmission and UL transmission may be needed, so there may be flexiblesymbols that cannot be used for UL transmission or DL transmission. Inmore detail, the n flexible symbols continuously located immediatelybefore the UL symbol may correspond to the guard period for DL-ULswitching or may be substantially allocated as a UL symbol, but may notbe substantially allocated as a DL symbol. In addition, the UE maydetermine that n flexible symbols continuously located immediatelybefore the OFDM symbol configured as the UL symbol by the RRC signal andthe UL symbol configured by the RRC signal are not included in thereference DL resource. The UE may determine the reference DL resource,excluding OFDM symbols configured as the DL symbol by the RRC signalamong OFDM Symbols between preemption indicator monitoring periods and nsymbols configured as the flexible symbol by the RRC signal andcontinuously located immediately before the UL symbol. In this case, nmay be 1. In addition, n may be 2 or more. In addition, the base stationmay signal the value of n using the RRC signal. In this case, the UE maydetermine the value of n based on the RRC signal. In addition, the RRCsignal may include a cell-specific RRC signal and may not include aUE-specific RRC signal in the ‘OFDM symbol configured as the UL symbolby the RRC signal among the OFDM symbols within the preemption indicatortransmission period’. In another specific embodiment, the RRC signal mayinclude both the cell-specific RRC signal and the UE-specific RRC signalin the ‘OFDM symbol configured as the UL symbol by the RRC signal amongthe OFDM symbols within the preemption indicator transmission period’.

The NR system may reserve some resources for forward compatibility orbackward compatibility. Such a resource is referred to as a reservedresource. The reserved resources may be used for DL transmission or ULtransmission. Therefore, the reference DL resource may be configured inconsideration of the reserved resource. This will be described withreference to FIGS. 24 to 26.

FIGS. 24 to 26 show OFDM symbols indicated by a preemption indicatoraccording to an embodiment of the present invention in relation to areserved resource.

In the above-described embodiments, the UE may exclude a symbol mappedto the reserved resource from the reference DL resource. In more detail,the UE may exclude from the reference DL resource an OFDM symbol inwhich all PRBs of the OFDM symbol are configured as reserved resources.

In FIG. 24, some PRBs of some of the OFDM symbols in the preemptionindicator transmission period are configured as reserved resources.Therefore, the UE determines that the reference DL resource includes thecorresponding symbols. In FIG. 25, all PRBs of some of the OFDM symbolsin the preemption indicator transmission period are configured asreserved resources. Therefore, the UE determines that the reference DLresource does not include the corresponding symbols.

In another specific embodiment, the UE may exclude the symbol mapped tothe reserved resource from the reference DL resource based on thefrequency domain to which the reserved resource is mapped. In moredetail, the reference DL resource may be divided in the frequency domainaccording to the frequency domain granularity used in the preemptionindicator. When the reference DL resource is divided in the frequencydomain, the UE may exclude from the reference DL resource an OFDM symbolin which all PRBs are configured as reserved resources for each dividedfrequency domain.

In FIG. 26, the frequency domain granularity is half of the PRB occupiedby the reference DL resource. Therefore, the reference DL resource isdivided into two regions along the dotted line. There is an OFDM symbolcorresponding to the reference DL resource above the dotted line amongthe OFDM symbols within the preemption indicator transmission period, inwhich all PRBs are configured as reserved resources. Accordingly, the UEexcludes the corresponding symbols from the reference DL resource. Thereis no OFDM symbol corresponding to the reference DL resource below thedotted line among the OFDM symbols within the preemption indicatortransmission period, in which all PRBs are configured as reservedresources. However, there is an OFDM symbol corresponding to the lowerreference DL resource among the OFDM symbols within the preemptionindicator transmission period, in which some PRBs are configured asreserved resources. Accordingly, the UE does not exclude thecorresponding symbol from the reference DL resource in the DL resource.

In another specific embodiment, the UE may determine the reference DLresource regardless of whether all PRBs of the OFDM symbol areconfigured as reserved resources. In more detail, the UE may exclude anOFDM symbol configured as the reserved resource for the UE from thereference DL resource. A PRB configured as a reserved resource may beconfigured by a cell-specific RRC signal.

In the 3GPP NR system, the UE may perform random access using the PRACH.The UE may determine the reference DL resource in relation to the PRACHtransmission. A method for the UE to determine a reference DL resourcein relation to a PRACH transmission is described below.

The PRACH for the UE may be configured by the base station. The UE mayobtain information on the PRACH configuration for the UE from theremaining minimum system information (RSI). The information on the PRACHconfiguration may include information on the PRACH transmissionparameter configuration. In more detail, the information on the PRACHtransmission parameter configuration may include at least one of a PRACHpreamble format configuration, a time resource configuration fortransmitting the PRACH, and a frequency resource configuration fortransmitting the PRACH. In addition, the information on the PRACHconfiguration may include information on the configuration of the rootsequence and the cyclic shift value of the PRACH preamble.

In addition, the UE may change the conditions that the UE transmits thePRACH depending on whether the UE transmits the PRACH in a carrier (orcell) using a frequency band of over 6 GHz. A carrier using a frequencyband of below 6 GHz is referred to as an FR1 carrier, and a carrierusing a frequency band of over 6 GHz is referred to as an FR2 carrier. AUE configured as a semi-static DL/UL configuration may transmit a PRACHonly in a UL symbol in a FR1 carrier (or cell). When the time resourceconfigured for the PRACH overlaps a DL symbol or a flexible symbol, a UEfor which semi-static DL/UL configuration is configured cannot transmita corresponding PRACH in an FR1 carrier (or cell). The UE for which thesemi-static DL/UL configuration is configured may transmit the PRACHonly in the UL symbol and the flexible symbol in the FR2 carrier (orcell). When the time resource configured for the PRACH overlaps the DLsymbol, the UE for which the semi-static DL/UL configuration isconfigured cannot transmit the corresponding PRACH in the FR1 carrier(or cell). In addition, if the PRACH is ahead of the SS/PBCH block inthe FR2 carrier (or cell), the UE cannot transmit the PRACH.

When the UE determines the reference DL resource indicated by thepreemption indicator in the FR2 carrier (or cell), the UE may determinethat the reference DL resource does not include an OFDM symbolconfigured for PRACH transmission. In this case, the UE may obtaininformation on an OFDM symbol configured for PRACH transmission based onthe RMSI described above. In more detail, the UE may obtain aPRACHConfigurationIndex which is a cell-specific RRC signal from theRMSI.

In another specific embodiment, when the UE determines the reference DLresource indicated by the preemption indicator in the FR1 carrier (orcell) and the FR2 carrier (or cell), the UE may determine that thereference DL resource does not include an OFDM symbol configured forPRACH transmission. In this case, the UE may obtain information on anOFDM symbol configured for PRACH transmission based on the RMSIdescribed above. In more detail, the UE may obtain aPRACHConfigurationIndex which is a cell-specific RRC signal from theRMSI.

In the 3GPP NR system, information required for the UE to receive theSS/PBCH block may be configured by the base station. The UE maydetermine the reference DL resource in relation to the SS/PBCH block. Amethod for the UE to determine a reference DL resource in relation to anSS/PBCH block is described below.

Information required to receive the SS/PBCH block may be configured by acell-specific RRC signal. In more detail, information required toreceive the SS/PBCH block may be configured by SSB-transmitted-SIB1 of acell-specific RRC signal. In addition, the information required toreceive the SS/PBCH block may be configured by a UE-specific RRC signal.In more detail, information required to receive the SS/PBCH block may beconfigured by SSB-transmitted of a UE-specific RRC signal. When the UEdoes not obtain the information necessary to receive the SS/PBCH blockfrom the cell-specific RRC signal and the UE-specific RRC signal, the UEmay monitor the SS/PBCH block at a predetermined location. If the UEobtains SSB-transmitted-SIB1 and fails to obtain SSB-transmitted, the UEmay monitor the SS/PBCH block configured in SSB-transmitted-SIB1. If theUE obtains SSB-transmitted, the UE may monitor the SS/PBCH blockconfigured in SSB-transmitted.

The UE may add the OFDM symbol configured as the DL SS/PBCH block to thereference DL resource. As described above, the symbol configured as theDL SS/PBCH block may be configured by at least one ofSSB-transmitted-SIB1, which is a cell-specific RRC signal, andSSB-transmitted, which is a UE-specific RRC signal. In more detail, theUE may add, to the reference DL resource, a symbol configured as anSS/PBCH block by the cell-specific RRC signal among OFDM symbols notincluded in the reference DL resource.

In a specific embodiment, in the cell (or carrier) of FR1, the UE maydetermine that the reference DL resource does not include the OFDMsymbol configured as the UL symbol by the cell-specific RRC signalwithout being configured as the SS/PBCH block. The UE may determine, asa reference DL resource, a DL symbol configured by the cell-specific RRCsignal among OFDM symbols between preemption monitoring periods, aflexible symbol configured by the cell-specific RRC signal, and an OFDMsymbol configured as an SS/PBCH block among UL symbols configured by thecell-specific RRC signal.

In a cell (or carrier) of FR2, the UE may determine that the referenceDL resource does not include an OFDM symbol configured as a UL symbol bya cell-specific RRC signal. The UE may determine that the reference DLresource does not include an OFDM symbol for ‘actual PRACH transmission’among the OFDM symbols configured as the PRACH. In this specification,‘actual PRACH transmission’ refers to a PRACH actually transmitted bythe UE according to the PRACH transmission condition described aboveamong PRACHs configured for the UE. In addition, as described above, theOFDM symbol may be configured as a PRACH by the cell-specific RRCsignal. In this case, the cell-specific RRC signal may be RMSI.Specifically, the UE may determine, as a reference DL resource, DLsymbols configured by the cell-specific RRC signal among OFDM symbolsbetween preemption monitoring periods, and flexible symbols configuredby the cell-specific RRC signal except for OFDM symbols for actual PRACHtransmission.

In such embodiments, the UE may determine that the reference DL resourcedoes not include the OFDM symbol configured as the PRACH without beingconfigured as the SS/PBCH block. Specifically, the UE may determine, asa reference DL resource, DL symbols configured by a cell-specific RRCsignal among OFDM symbols between preemption monitoring periods,flexible symbols configured by the cell-specific RRC signal except forOFDM symbols configured as PRACH, and OFDM symbols configured as anSS/PBCH block. When the OFDM symbol configured as the SS/PBCH blockconfigured by the RRC signal and the OFDM symbol configured as the PRACHoverlap, the UE may regard the OFDM symbol as a DL symbol. When the OFDMsymbol configured as the SS/PBCH block configured by the RRC signal andthe OFDM symbol configured as the PRACH overlap, the UE may determinethat the reference DL resource includes the corresponding OFDM symbol.

In the above embodiment, the UE may determine the reference DL resourcebased on the OFDM symbol for ‘actual PRACH transmission’, rather thanthe OFDM symbol configured as the PRACH. In more detail, the UE maydetermine that the reference DL resource does not include the OFDMsymbol configured as the OFDM symbol for actual PRACH transmissionwithout being configured as the SS/PBCH block. In a specific embodiment,the UE may determine, as a reference DL resource, DL symbols configuredby a cell-specific RRC signal among OFDM symbols between preemptionmonitoring periods, flexible symbols configured by the cell-specific RRCsignal except for OFDM symbols configured for actual PRACH transmission,and OFDM symbols configured as an SS/PBCH block.

In the above-described three embodiments, it is described that the UEdetermines a reference DL resource in FR2. The UE may determine thereference DL resource according to the three embodiments described abovein FR1 as well as FR2.

The base station may signal the reference DL resource for eachpreemption indicator using a period of monitoring for the preemptionindicator and an offset. The UE may determine the reference DL resourcefor each preemption indicator based on the period of monitoring for thepreemption indicator and the offset. In more detail, the UE maydetermine the index of the OFDM symbol corresponding to the reference DLresource by using the following equation.{mT _(INT)−Δ_(offset) ,mT _(INT)+1−Δ_(offset), . . . ,(m+1)T_(INT)−1−Δ_(offset)}

In this case, {mT_(INT), mT_(INT)+1, . . . , (m+1)T_(INT)−1} is an indexof an OFDM symbol between periods of monitoring for the preemptionindicator. Also, Δ_(offset) is an offset. The offset may have any one of0, 14, and T_(INT) values. In addition, the offset may be configured bythe RRC signal.

When the preemption indicator indicates whether one OFDM symbol ispreempted per bit, the overhead of the preemption indicator may beexcessively large. In a specific embodiment, it may be assumed that aslot includes 14 OFDM symbols and a preemption indicator indicateswhether the preemption occurs in an OFDM symbol included in 4 slots. Inthis case, when the preemption indicator indicates whether one OFDMsymbol is preempted per one bit, the preemption indicator may use 56bits in total. The base station may configure the preemption indicatorsuch that one bit of the preemption indicator indicates whether thepreemption occurs in one or more OFDM symbols. For example, one bit ofthe preemption indicator may indicate whether the preemption occurs infour OFDM symbols. When it is assumed that a slot includes 14 OFDMsymbols and a preemption indicator indicates whether the preemptionoccurs in an OFDM symbol included in 4 slots, the preemption indicatorrequires 14 bits. The preemption indicator may divide the entire OFDMsymbol corresponding to the reference DL resource into a plurality ofgroups each indicating one or more OFDM symbols, and indicate by one bitwhether the preemption occurs in each group. In this case, the UE maydetermine that transmission from the base station to the UE does notoccur in at least one OFDM symbol corresponding to the correspondinggroup according to the value of each bit of the preemption indicator. Inaddition, the UE may determine that transmission from the base stationto the UE occurs in at least one OFDM symbol corresponding to thecorresponding group according to the value of each bit of the preemptionindicator. A method of dividing the entire OFDM symbol corresponding tothe reference DL resource into a plurality of groups each indicating oneor more OFDM symbols will be described with reference to FIGS. 27 to 29.

FIG. 27 shows an OFDM symbol indicating whether a bitmap of a preemptionindicator is preempted according to an embodiment of the presentinvention.

When the reference DL resource includes S OFDM symbols and thepreemption indicator has a length of N-bits, a method of dividing the SOFDM symbols into N groups and indicating whether there is a preemptionin the S OFDM symbols by N-bits will be described. In this case, the UEmay determine that transmission from the base station to the UE occursor does not occur in all OFDM symbol(s) belonging to the groupcorresponding to the corresponding bit according to the value of eachbit among the N-bits of the preemption indicator. In detail, when anyone of the N-bits of the preemption indicator is the first value, the UEmay determine that transmission from the base station to the UE occursin all of one or more OFDM symbols belonging to the group correspondingto the corresponding bit. In addition, when any one of the N-bits of thepreemption indicator is the second value, the UE may determine thattransmission from the base station to the UE does not occur in all ofone or more OFDM symbols belonging to the group corresponding to thecorresponding bit. Therefore, the UE additionally receives a preemptionindicator in the resource scheduled for the UE by the base station, anddepending on the determination of whether the transmission from the basestation to the UE occurs according to the preemption, the UE performsdecoding the resource scheduled for the UE by the base station. In moredetail, the UE may determine that transmission from the base station tothe UE occurs in all OFDM symbols of a specific OFDM symbol groupaccording to the preemption indicator. In this case, the UE may performdecoding and combining (binding) one or more OFDM symbols including thecorresponding OFDM symbol group in the resource scheduled for the UE. Inaddition, the UE may determine, according to the preemption indicator,that transmission from the base station to the UE does not occur by apreemption in all OFDM symbols of a specific OFDM symbol group. In thiscase, the UE may perform decoding and combining (binding) one or moreOFDM symbols excluding the corresponding OFDM symbol(s) in the scheduledresource.

When the preemption indicator includes a bitmap indicating whether theOFDM symbol group corresponding to each bit is preempted, the basestation may explicitly signal the index of the OFDM symbol indicated byeach bit of the bitmap using the RRC signal. The UE may obtain the indexof the OFDM symbol indicated by each bit of the bitmap included in thepreemption indicator based on the RRC signal. In another specificembodiment, the UE may determine the OFDM symbol indicated by each bitof the bitmap included in the preemption indicator according to apredetermined rule.

In addition, the base station may divide the S OFDM symbols into Ngroups according to the following method, and may indicate whether thereis a preemption for each of the N groups. In this case, the UE maydetermine whether there is a preemption for each of the N groups basedon the preemption indicator. In this case, the S OFDM symbolscorresponding to the DL reference resource may be grouped into N groupsof C OFDM symbols in time order. In this case, C may be determined bythe following equation.C=ceil(S/N)

When S OFDM symbols are indexed and displayed in time order from 1 to N,N OFDM symbols may be represented as grouped as follows. The first groupis {1, 2, . . . , C}, the second group is {C+1, C+2, . . . , 2*C}, . . ., the (N−1)-th group is {(N−2)*C+1, (N−2)*C+2, . . . , (N−1)*C}, andN-th group is {(N−1)*C, (N−1)*C+1, . . . , S}.

In another specific embodiment, the difference between the number ofOFDM symbols included in each group may be at most 1. Among the Ngroups, each of the mod(S, N) groups may include ceil(S/N) OFDM symbols,and each of the remaining (N−mod(S,N)) groups may include floor(S/N)OFDM symbols. In this case, mod(a,b) represents the remainder when a isdivided by b. Unless otherwise specified herein, mod(a, b) representsthe remainder when a is divided by b. floor(x) represents the largestinteger equal to or less than x. Unless otherwise specified herein,floor(x) represents the largest integer equal to or less than x.

As described above, the OFDM symbol included in the reference DLresource may be discontinuous. In this case, the S OFDM symbols includedin the reference DL resource is indexed in a time sequence as whencontinuous, S OFDM symbols may be divided into N groups according to theabove-described two embodiments. However, in this embodiment, aplurality of discontinuous OFDM symbols may be classified into onegroup. In addition, the probability that a plurality of discontinuousOFDM symbols are punctured by preemption at the same time may be sparse.Nevertheless, preemption may be signaled in one group.

In another specific embodiment, the S OFDM symbols included in thereference DL resource may be grouped into M groups including continuousOFDM symbols. In more detail, the individual groups may include onlycontinuous OFDM symbols. For the convenience of description, the numberof OFDM symbols included in each group is indicated by S₁, S₂, . . . ,S_(M). In addition, the number of bits of the preemption indicatorcorresponding to each group is indicated by N₁, N₂, . . . , N_(M). Inthis case, N₁+N₂+ . . . +N_(M)=N is satisfied. The number of bits of thepreemption indicator corresponding to each group may be determined basedon the number of OFDM symbols included in each group. In more detail,the number of bits of the preemption indicator corresponding to eachgroup may be proportional to the number of OFDM symbols included in eachgroup. Specifically, in the remaining groups except for the last group,the number of bits of the preemption indicator corresponding to eachgroup may be determined according to the following equation.N _(i)=round((N−M)*S _(i) /S)+1

In this case, i represents the index of each group. In addition,round(x) represents an integer closest to x. Unless otherwise mentionedin this specification, round(x) represents an integer closest to x. Inaddition, round(x) may be changed to floor(x) indicating a round downoperation or ceil(x) indicating a round up operation.

In the case of the last group, the number of bits of the preemptionindicator corresponding to the last group may be determined according tothe following equation.N _(M) =N−(N ₁ +N ₂ + . . . +N _(M−1)).

In another specific embodiment, in the case of the remaining groupsexcept for the last group, the number of bits of the preemptionindicator corresponding to each group may be determined according to thefollowing equation.N _(i)=round(N*S _(i) /S)In this case, i represents the index of each group. In addition,round(x) represents an integer closest to x. In addition, round(x) maybe changed to floor(x) indicating a round down operation or ceil(x)indicating a round up operation.

The number of bits of the preemption indicator corresponding to the lastgroup may be determined according to the following equation.N _(M) =N−(N ₁ +N ₂ + . . . +N _(M−1)).

In the embodiments described above, each group includes continuous OFDMsymbols. However, OFDM symbols included in different slots may beincluded together in one group. For example, the last OFDM symbol of the(n−3)-th slot and the first OFDM symbol of the (n−2)-th slot may beincluded in one group. Different transport blocks (TBs) may be allocatedto OFDM symbols included in different slots. Therefore, in a specificembodiment, each group may include only OFDM symbols included in the oneslot. For example, the UE and the base station may regard the OFDMsymbols included in different slots as discontinuous in relation to thegrouping of the preemption indicator.

In the above-described embodiments, the order of the group index may bedetermined according to the time order of the OFDM symbols included inthe group. Therefore, the first group may include S₁ OFDM symbolscontinuously located first in the reference DL resource. In addition,the last group may include continuous S_(M) OFDM symbols located last intime in the reference DL resource. In another specific embodiment, theorder of the group indexes may be determined in ascending order from intime order of OFDM symbols included in each group. Therefore, the firstgroup may include the least number of OFDM symbols and the last groupmay include the largest number of OFDM symbols. In another specificembodiment, the order of the group indexes may be determined indescending order from in time order of OFDM symbols included in eachgroup. Therefore, the first group may include the largest number of OFDMsymbols and the last group may include the least number of OFDM symbols.When the number of continuous symbols is the same, the preceding groupmay include an OFDM symbol located first in the time domain. Someembodiments of the above-described embodiments will be described indetail with reference to FIG. 27.

In the embodiment of FIG. 27, the base station transmits a controlchannel including a preemption indicator every two slots. Each slotincludes 14 OFDM symbols. Accordingly, the preemption indicatortransmitted in the n-th slot indicates whether the DL resource ispunctured by the preemption in the (n−2)-th slot and the (n−1)-th slot.In FIG. 27, when the preemption indicator corresponds to the first typeType #1, the preemption indicator indicates all OFDM symbols included inthe slot. Accordingly, the preemption indicator divides a total of 28OFDM symbols into N groups and allows only one difference in the numberof OFDM symbols included in each group. When N is 4, the preemptionindicator indicates 4 groups including 7 OFDM symbols. In this case, thefirst bit of the preemption indicator indicates whether at least oneOFDM symbol among the OFDM symbols from the first OFDM symbol to theseventh OFDM symbol of the (n−2)-th slot is punctured by the preemption.In addition, the second bit of the preemption indicator indicateswhether at least one OFDM symbol among the OFDM symbols from the secondOFDM symbol to the fourteenth OFDM symbol of the (n−2)-th slot ispunctured by the preemption. Furthermore, the third bit of thepreemption indicator indicates whether at least one OFDM symbol amongthe OFDM symbols from the first OFDM symbol to the seventh OFDM symbolof the (n−1)-th slot is punctured by the preemption. In addition, thefourth bit of the preemption indicator indicates whether at least oneOFDM symbol among the OFDM symbols from the second OFDM symbol to thefourteenth OFDM symbol of the (n−1)-th slot is punctured by thepreemption. However, since the eighteenth to fourteenth OFDM symbols inthe (n−1)-th slot are not used as DL resources, the fourth bit of thepreemption indicator indicates unnecessary information.

In FIG. 27, when the preemption indicator corresponds to the second typeType #2 or the third type Type #3, the preemption indicator indicatesonly OFDM symbols that can be preempted among the OFDM symbols includedin the slot. In this case, the UE may determine the reference DLresource based on the configuration or RRC signal of the OFDM symbolincluded in the slot. The first OFDM symbol to the tenth OFDM symbol ofthe (n−2)-th slot, and the first OFDM symbol and the second OFDM symbolof the (n−1)-th slot correspond to the reference DL resources.Therefore, the number of OFDM symbols indicated by the preemptionindicator is 12. If the preemption indicator corresponds to the secondtype Type #2, the plurality of OFDM symbols corresponding to thereference DL resources are grouped regardless of whether the OFDMsymbols included in one group are continuous. In addition, thedifference in the number of OFDM symbols included in each group may beup to one. Specifically, 12 OFDM symbols are divided into four groupseach including three OFDM symbols. Specifically, the first bit of thebitmap of the preemption indicator indicates whether at least one OFDMsymbol among the OFDM symbols from the first OFDM symbol to the thirdOFDM symbol of the (n−2)-th slot is punctured by the preemption. Inaddition, the second bit of the bitmap of the preemption indicatorindicates whether at least one OFDM symbol among the OFDM symbols fromthe fourth OFDM symbol to the sixth OFDM symbol of the (n−2)-th slot ispunctured by the preemption. In addition, the third bit of the bitmap ofthe preemption indicator indicates whether at least one OFDM symbolamong the OFDM symbols from the seventh OFDM symbol to the ninth OFDMsymbol of the (n−2)-th slot is punctured by the preemption. In addition,the second bit of the bitmap of the preemption indicator indicateswhether at least one OFDM symbol among OFDM symbols from the tenth OFDMsymbol of the (n−2)-th slot and the first OFDM symbol of the (n−1)-thslot to the second OFDM symbol of the (n−1)-th slot is punctured by thepreemption. In the embodiment of FIG. 27, when the preemption indicatorcorresponds to the second type Type #2, unlike the case where thepreemption indicator corresponds to the first type Type #1, thepreemption indicator does not indicate unnecessary information. However,the fourth group includes OFDM symbols included in different slots.Accordingly, the preemption indicator indicates whether the OFDM symbolsincluded in different slots are preempted with one bit. This second typeType #2 method allows the delivery of a preemption indicator in aresource that may substantially be preempted, so that it is possible forthe UE to prevent a reduction in the data transfer rate caused bydecoding and combining a resource that is not likely to be unnecessarilypreempted under the assumption that no transmission occurs from the basestation.

When the preemption indicator corresponds to the third type Type #3, aplurality of OFDM symbols corresponding to the reference DL resource aregrouped under the assumption that all OFDM symbols included in one groupare continuous. In the embodiment of FIG. 27, they are divided into 10continuous OFDM symbols and 2 OFDM symbols. In this case, the bit numberN1 of the preemption indicator indicating 10 continuous OFDM symbols maybe obtained based on the following equation.N ₁=round((N−2)*S ₁ /S)+1

In this case, S is the total number of OFDM symbols corresponding to theDL reference resource. In addition, S₁ is the number of first continuousOFDM symbols. In addition, N is the total number of bits of thepreemption indicator. Therefore, when the preemption indicatorcorresponds to the third type Type #3, ten OFDM symbols are indicated by3 bits and two OFDM symbols are indicated by 1-bit. Specifically, thefirst bit of the bitmap of the preemption indicator indicates whether atleast one OFDM symbol among the OFDM symbols from the first OFDM symbolto the fourth OFDM symbol of the (n−2)-th slot is punctured by thepreemption. In addition, the second bit of the bitmap of the preemptionindicator indicates whether at least one OFDM symbol among the OFDMsymbols from the fifth OFDM symbol to the seventh OFDM symbol of the(n−2)-th slot is punctured by the preemption. In addition, the third bitof the bitmap of the preemption indicator indicates whether at least oneOFDM symbol among the OFDM symbols from the eighth OFDM symbol to thetenth OFDM symbol of the (n−2)-th slot is punctured by the preemption.In addition, the fourth bit of the bitmap of the preemption indicatorindicates whether at least one OFDM symbol among the OFDM symbols fromthe first OFDM symbol of the (n−1)-th slot to the second OFDM symbol ofthe (n−1)-th slot is punctured by the preemption. When the preemptionindicator corresponds to the third type Type #3, unlike the case wherethe preemption indicator corresponds to the second type Type #2, OFDMsymbols included in different slots are not indicated by one bit. Thissecond type Type #2 method allows the delivery of a preemption indicatorin a resource that may substantially be preempted, so that it ispossible for the UE to prevent a reduction in the data transfer ratecaused by decoding and combining a resource that is not likely to beunnecessarily preempted under the assumption that no transmission occursfrom the base station. In addition, when the transmission for thetransport block (TB) in different slots occurs at the same time, it isunlikely that preemption will occur discontinuously in different slots.Therefore, when the base station follows this embodiment, it is possibleto more precisely indicate to the UE the resources that are likely to bepreempted.

FIG. 28 shows an OFDM symbol indicating whether a bitmap of a preemptionindicator is preempted according to another embodiment of the presentinvention.

In another specific embodiment of the present invention, the basestation may classify a reference DL resource into a plurality ofsub-reference DL resources, and indicate whether there is a preemptionby classifying the sub-reference DL resources into a plurality ofgroups. In more detail, the preemption indicator may indicate onesub-reference DL resource among a plurality of sub-reference DLresources included in the reference DL resource, and indicate whetherthere is a preemption for each of a plurality of groups included in thesub-reference DL resource. In this case, the preemption indicator mayinclude a first field indicating one of a plurality of sub-reference DLresources and a second field indicating whether a plurality of groupsincluded in the indicated sub-reference DL resource are preempted. Inthis case, the second field may be configured according to the bitmapconfiguration method of the preemption indicator described above inother embodiments. The UE may determine a sub-reference DL resourceindicated by the preemption indicator based on the preemption indicator,and determine whether a plurality of groups included in thesub-reference DL resource are preempted based on the preemptionindicator. In more detail, the UE may determine a sub-reference DLresource indicated by the preemption indicator based on the first field,and may determine whether a plurality of groups included in thesub-reference DL resource are preempted based on the second field. Thesub-reference DL resource may include a specified number of OFDMsymbols. In this case, the specified number may be the number of OFDMsymbols included in one slot. In addition, the sub-reference DL resourcemay be limited to include only continuous OFDM symbols.

In the embodiment of FIG. 28, the first bit of the preemption indicatorindicates a sub-reference DL resource in which the preemption occurs,and the second bit indicates whether the preemption occurs in each of aplurality of groups included in the sub-reference DL resource. In thiscase, the first sub-reference DL resource is a set of OFDM symbolslocated in the (n−2)-th slot of the reference DL resource. In addition,the second sub-reference DL resource is a set of OFDM symbols located inthe (n−1)-th slot of the reference DL resource. When the preemptionindicator indicates the first sub-reference DL resource, the first bitof the second bit bitmap of the preemption indicator indicates whetherat least one OFDM symbol among the OFDM symbols from the first OFDMsymbol to the fifth OFDM symbol of the (n−2)-th slot is punctured by thepreemption. In addition, when the preemption indicator indicates thefirst sub-reference DL resource, the second bit of the second bit bitmapof the preemption indicator indicates whether at least one OFDM symbolamong the OFDM symbols from the sixth OFDM symbol to the tenth OFDMsymbol of the (n−2)-th slot is punctured by the preemption. In addition,when the preemption indicator indicates the second sub-reference DLresource, the first bit of the second bit bitmap of the preemptionindicator indicates whether the first OFDM symbol of the (n−1)-th slotis punctured by the preemption. In addition, when the preemptionindicator indicates the second sub-reference DL resource, the second bitof the second bit bitmap of the preemption indicator indicates whetherthe second OFDM symbol of the (n−1)-th slot is punctured by thepreemption.

In the embodiment of FIG. 28, the UE additionally receives the first bitand the second bit as a preemption indicator within the resourcescheduled to the UE by the base station to determine whether apreemption occurs in each of a plurality of groups includingsub-reference DL resources indicated by the base station. In this case,the UE may perform decoding on the scheduled resource according to thedetermination of whether the transmission from the base station to theUE occurs.

FIG. 29 shows an OFDM symbol indicating whether a bitmap of a preemptionindicator is preempted according to another embodiment of the presentinvention.

The base station may signal to the UE how many OFDM symbols areconfigured in one group among groups to be indicated through thepreemption indicator using the RRC configuration. In more detail, thebase station may signal a time-domain OFDM symbol granularity to the UEusing an RRC configuration. The UE may determine how many OFDM symbolsthe preemption indicator configures in one group based on the RRCsignal. In addition, the UE may determine the OFDM symbol groupindicated by each bit of the bitmap of the preemption indicator based onthe OFDM symbol configuration included in the slot and how many OFDMsymbols are configured in one group by the preemption indicator. Whenthe reference DL resource includes S OFDM symbols and the OFDM symbolgranularity is C, the UE may determine that ceil(S/C) bits are used asthe bitmap in the preemption indicator. In this case, it is assumed thatthe preemption indicator indicates S OFDM symbols in sequence. In thiscase, when 1≤i<ceil(S/C) is satisfied, the UE may determine that thei-th bit of the bitmap of the preemption indicator indicates whether atleast one OFDM symbol among the (C*(i−1)+1)-th OFDM symbol, . . . , the(C*i)-th OFDM symbol is punctured by the preemption. Moreover, when isatisfies i=ceil(S/C), the UE may determine that the i-th bit of thepreemption indicator indicates whether at least one OFDM symbol amongthe (C*(i−1)+1)-th OFDM symbol, . . . , the S-th OFDM symbol ispunctured by the preemption. In addition, the preemption indicator mayinclude a bit indicating which PRB is punctured by the preemption.

In the embodiment of FIG. 29, the first OFDM symbol to the tenth OFDMsymbol of the (n−2)-th slot, and the first OFDM symbol and the secondOFDM symbol of the (n−1)-th slot correspond to the reference DLresources. In this case, the OFDM symbol granularity is three. In thefirst case case #1, the preemption indicator includes a 4-bit bitmap.The first bit of the bitmap of the preemption indicator indicateswhether at least one OFDM symbol among the OFDM symbols from the firstOFDM symbol to the third OFDM symbol of the (n−2)-th slot is puncturedby the preemption. In addition, the second bit of the bitmap indicateswhether at least one OFDM symbol among the OFDM symbols from the fourthOFDM symbol to the sixth OFDM symbol of the (n−2)-th slot is puncturedby the preemption. In addition, the third bit of the bitmap indicateswhether at least one OFDM symbol among the OFDM symbols from the seventhOFDM symbol to the ninth OFDM symbol of the (n−2)-th slot is puncturedby the preemption. In addition, the fourth bit of the bitmap indicateswhether at least one OFDM symbol among the tenth OFDM symbol of the(n−2)-th slot, and the first OFDM symbol and the second OFDM symbol ofthe (n−1)-th slot is punctured by the preemption.

In the above-described embodiments, each group may be limited to includeonly continuous OFDM symbols. In this case, the UE may determine theOFDM symbol group indicated by each bit of the bitmap of the preemptionindicator on the premise that each group includes only continuous OFDMsymbols. For example, it may be assumed that the reference DL resourceincludes S OFDM symbols and S₁ OFDM symbols among the S OFDM symbols arecontinuous. In this case, the OFDM symbol granularity signaled by theRRC signal is C. The UE may determine that ceil(S₁/C)+ceil(S₂/C) bitsare used in the preemption indicator. In more detail, when1≤i<ceil(S₁/C) is satisfied, the UE may determine that the i-th bit ofthe bitmap of the preemption indicator indicates whether at least oneOFDM symbol among the (C*(i−1)+1)-th OFDM symbol, . . . , the (C*i)-thOFDM symbol is punctured by the preemption. Moreover, when i satisfiesceil(S₁/C)+1≤i<ceil(S₁/C)+ceil(S₂/C), the UE may determine that the i-thbit of the bitmap of the preemption indicator indicates whether at leastone OFDM symbol among the (S₁+C*(i−1)+1)-th OFDM symbol, . . . ,(S₁+C*i)-th OFDM symbol is punctured by the preemption. Wheni=ceil(S₁/C)+ceil(S₂/C) is satisfied, the UE may determine that the i-thbit of the bitmap of the preemption indicator indicates whether at leastone OFDM symbol among the (S₁+C*(i−1)+1)-th OFDM symbol, . . . , the(S₁+S₂)-th OFDM symbol is punctured by the preemption.

In the second case case #2 of the embodiment of FIG. 29, the preemptionindicator includes a 5-bit bitmap. The first bit of the bitmap of thepreemption indicator indicates whether at least one OFDM symbol amongthe OFDM symbols from the first OFDM symbol to the third OFDM symbol ofthe (n−2)-th slot is punctured by the preemption. In addition, thesecond bit of the bitmap indicates whether at least one OFDM symbolamong the OFDM symbols from the fourth OFDM symbol to the sixth OFDMsymbol of the (n−2)-th slot is punctured by the preemption. In addition,the third bit of the bitmap indicates whether at least one OFDM symbolamong the OFDM symbols from the seventh OFDM symbol to the ninth OFDMsymbol of the (n−2)-th slot is punctured by the preemption. In addition,the fourth bit of the bitmap indicates whether the tenth OFDM symbol ofthe (n−2)-th slot is punctured by the preemption. In addition, the fifthbit of the bitmap indicates whether at least one OFDM symbol among thefirst OFDM symbol and the second OFDM symbol of the (n−1)-th slot ispunctured by the preemption. This second case case #2 allows thedelivery of a preemption indicator in a resource that may besubstantially preempted. Accordingly, in the second case case #2, thebase station can prevent a reduction in data transfer rate that occursas the UE decodes and combines resources that are not likely to bepreempted unnecessarily under the assumption transmission does not occurfrom the base station. In addition, when the transmission for thetransport block (TB) in different slots occurs at the same time, it isunlikely that preemption will occur discontinuously in different slots.Accordingly, in this embodiment, the base station can more preciselyindicate to the UE the resources that are likely to be preempted.

In the same OFDM symbol configuration, the UE may determine the OFDMsymbol group indicated by each bit of the bitmap of the preemptionindicator according to the following embodiment. S₁ OFDM symbols may bedivided into N₁=ceil(S₁/C) groups. In this case, each of the firstmod(S₁, N₁) groups of ceil(S₁/C) groups may include C OFDM symbols, andeach of the remaining N₁−mod(S₁, N₁) groups may include C−1 OFDMsymbols. In addition, the S₂ OFDM symbols may be divided intoN₂=ceil(S₂/C) groups. In this case, each of the first mod(S₂, N₂) groupsof ceil(S₂/C) groups may include C OFDM symbols, and each of theremaining N₂−mod(S₂, N₂) groups may include C−1 OFDM symbols.

In the third case case #3 of the embodiment of FIG. 29, the preemptionindicator includes a 5-bit bitmap. The first bit of the bitmap of thepreemption indicator indicates whether at least one OFDM symbol amongthe OFDM symbols from the first OFDM symbol to the third OFDM symbol ofthe (n−2)-th slot is punctured by the preemption. In addition, thesecond bit of the bitmap indicates whether at least one OFDM symbolamong the OFDM symbols from the fourth OFDM symbol to the sixth OFDMsymbol of the (n−2)-th slot is punctured by the preemption. In addition,the third bit of the bitmap indicates whether at least one OFDM symbolamong the OFDM symbols from the seventh OFDM symbol to the eighth OFDMsymbol of the (n−2)-th slot is punctured by the preemption. In addition,the fourth bit of the bitmap indicates whether at least one OFDM symbolamong the ninth OFDM symbol and the tenth OFDM symbol of the (n−2)-thslot is punctured by the preemption. In addition, the fifth bit of thebitmap indicates whether at least one OFDM symbol among the first OFDMsymbol and the second OFDM symbol of the (n−1)-th slot is punctured bythe preemption. In this third case case #3, the base station maytransmit a preemption indicator indicating a resource that may besubstantially preempted. Accordingly, the base station can prevent areduction in the data transfer rate that occurs as the UE decodes andcombines resources that are not likely to be preempted under theassumption that transmission does not occur from the base station. Inaddition, when the transmission for the transport block (TB) indifferent slots occurs at the same time, it is unlikely that preemptionwill occur discontinuously in different slots. Accordingly, the basestation can more precisely indicate to the UE the resources that arelikely to be preempted. In such an embodiment, the base station mayfurther equalize the division of resources in which the preemption mayoccur within the same slot to maximum in the OFDM symbol unit, that is,the length difference between OFDM symbols in each group is allowed tobe at least one. Accordingly, the base station can prevent a reductionin data transfer rate to maximum even when a small number of preemptionoccurs in the OFDM symbol unit.

In the embodiment of FIG. 29, the UE additionally receives a preemptionindicator within the resource scheduled for the UE by the base stationto determine whether a preemption occurs in each of a plurality ofgroups including reference DL resources indicated by the base station.The UE may perform decoding on the scheduled resource for the UEaccording to the determination of whether the transmission from the basestation to the UE occurs.

The UE may determine the payload size of the preemption indicator basedon the RRC signal. In more detail, the UE may determine the payload sizeof the preemption indicator explicitly or implicitly based on the RRCsignal. When the payload size of the preemption indicator is smallerthan the payload size indicated by the RRC signal, the base station mayadd the padding to the payload of the preemption indicator with someredundant value to adjust the payload size of the preemption indicatorand the payload size indicated by the RRC signal. An unnecessary valuemay be zero. In another specific embodiment, the redundant value may beone.

Reference DL resources may be divided into a plurality of groups in thefrequency domain as well as the time domain. An embodiment related tothis will be described.

When the reference DL resource includes S OFDM symbols and B PRBs, thereference DL resources may be divided into N in the time domain and F inthe frequency domain. S OFDM symbols may be divided into N groups, and BPRBs may be divided into F groups. Therefore, the reference DL resourcemay be divided into N×F groups. The preemption indicator includes N×Fbits, and the UE may determine that preemption occurs in a group ofreference DL resources in which each of the N×F bits corresponds to abit. In a specific embodiment, N=14 and F=1. It may also be N=7 and F=2.In this case, the base station may configure the values of N and F usingthe RRC signal. The UE may obtain values of N and F based on the RRCsignal.

When N=14 and F=1, the UE may divide the B PRBs into one group. Inaddition, when N=7 and F=2, the UE may divide ceil(B/2) PRBs among BPRBs into one group, and divide the remaining B-ceil(B/2) PRBs intoanother group. In another specific embodiment, when N=7 and F=2, the UEmay divide floor(B/2) PRBs among B PRBs into one group, and divide theremaining B−floor(B/2) PRBs into another group.

When the reference DL resource includes S OFDM symbols, the UE maydivide the reference DL resource into N groups according to thefollowing embodiments. If N≥S, the S OFDM symbols are divided into Sgroups, and each of the S×F bits of the preemption indicator mayindicate whether a preemption occurs in each group. In this case, thebase station may pad the remaining (N−S)×F bits of the preemptionindicator with a redundant value in order to make the size of thepreemption indicator into N×F bits. An unnecessary value may be zero. Inanother specific embodiment, the redundant value may be one. Specificembodiments when N<S are as follows. The UE may group C=floor(S/N) OFDMsymbols in order to divide the S OFDM symbols included in the referenceDL resource into N groups. When S OFDM symbols are indexed starting from1 in time order, N groups may be represented as follows. The first groupis {1.2, 2, . . . , C}, the second group is {C+1, C+2, . . . , 2*C}, . .. , the (N−1)-th group is {(N−2)*C+1, (N−2)*C+2, . . . , (N−1)*C}, andN-th group is {(N−1)*C, (N−1)*C+1, . . . , S}. In this case, the N-thgroup may include more than C OFDM symbols.

In order not to allow more than one difference in the number of OFDMsymbols included in each group, S OFDM symbols may be divided into Ngroups. When S OFDM symbols are indexed starting from 1 in time order, Ngroups may be divided as follows. Each of the first mod(S, N) groupsamong N groups may include ceil(S/N) OFDM symbols, and each of theremaining N−mod(S, N) groups may include floor(S/N) OFDM symbols. Inthis case, mod(S, N) may be expressed as S−floor(S/N)*N.

When the S OFDM symbols include discontinuous OFDM symbols in the timedomain, the S OFDM symbols may be divided into N groups according to thefollowing embodiments. S OFDM symbols may be divided into M groupsincluding continuous OFDM symbols in the time domain. The number of OFDMsymbols included in each group is referred to as S₁, S₂, . . . , S_(M).M groups may be further divided into a plurality of subgroups. Thenumber of subgroups included in each of the M groups is N₁, N₂, . . . ,N_(M). In this case, N₁+N₂+ . . . +N_(M)≤N is satisfied.

The i-th group may be divided into Ni subgroups according to thefollowing embodiments. The OFDM symbols included in the i-th group maybe divided into Ni subgroups including C_(i)=floor(S_(i)/N_(i)) OFDMsymbols. When Si OFDM symbols are indexed starting from 1 in time order,Ni subgroups may be represented as follows. The first group is {1, 2, .. . , Ci}, the second group is {C_(i)+1, C_(i)+2, . . . , 2*C_(i)}, the(N_(i)−1)-th group is {(N−2)*C_(i)+1, (N_(i)−2)*C_(i)+2, . . . ,(N_(i)−1)*C_(i)}, and the N_(i)-th group is {(N_(i)−1)*C_(i),(N_(i)−1)*C_(i)+1, . . . , S}. In this case, the N_(i)-th group mayinclude more than C_(i) OFDM symbols.

In this case, the number of OFDM symbols included in the Ni subgroups ofthe i-th group may be determined as in the following embodiments. Inmore detail, the number of OFDM symbols included in each of theplurality of subgroups included in the i-th group may be at most one.When Si OFDM symbols are indexed starting from 1 in time order, Nisubgroups may be divided as follows. Each of the first mod(S_(i), N_(i))groups of N_(i) groups may include ceil(S_(i)/N_(i)) OFDM symbols, andeach of the remaining N_(i)−mod(S_(i), N_(i)) groups may includefloor(S_(i)/N_(i)) OFDM symbols.

When an OFDM symbol corresponding to a reference DL resource is includedin two or more slots, according to the following embodiment, OFDMsymbols corresponding to reference DL resources may be classified into Ngroups. First, S OFDM symbols are classified into M groups includingcontinuous OFDM symbols for each slot. The number of OFDM symbolsincluded in each group is referred to as S₁, S₂, . . . , S_(M). M groupsmay be further divided into a plurality of subgroups. The number ofsubgroups included in each of the M groups is N₁, N₂, . . . , N_(M). Inthis case, N₁+N₂+ . . . +N_(M)≤N is satisfied.

The i-th group may be divided into Ni subgroups according to thefollowing embodiments. The OFDM symbols included in the i-th group maybe divided into Ni subgroups including Ci=floor(Si/Ni) OFDM symbols.When Si OFDM symbols are indexed starting from 1 in time order, Nisubgroups may be represented as follows. The first group is {1, 2, . . ., Ci}, the second group is {Ci+1, Ci+2, . . . , 2*Ci}, the (Ni−1)-thgroup is {(N−2)*Ci+1, (Ni−2)*Ci+2, . . . , (Ni−1)*Ci}, and the Ni-thgroup is {(Ni−1)*Ci, (Ni−1)*Ci+1, . . . , S}. In this case, the Ni-thgroup may include more than Ci OFDM symbols.

In this case, the number of OFDM symbols included in the Ni subgroups ofthe i-th group may be determined as in the following embodiments. Inmore detail, the number of OFDM symbols included in each of theplurality of subgroups included in the i-th group may be at most one.When Si OFDM symbols are indexed starting from 1 in time order, N_(i)subgroups may be divided as follows. Each of the first mod(S_(i), N_(i))groups of N_(i) subgroups may include ceil(S_(i)/N_(i)) OFDM symbols,and each of the remaining N_(i)−mod(Si/N_(i)) groups may includefloor(Si/Ni) OFDM symbols.

When the monitoring period of the preemption indicator is one slot ormore, and the OFDM symbol corresponding to the reference DL resourceincludes discontinuous OFDM symbols in the time domain, according to thefollowing embodiment, OFDM symbols corresponding to reference DLresources may be classified into N groups. First, S OFDM symbols areclassified into M groups including continuous OFDM symbols for eachslot. The number of OFDM symbols included in each group is referred toas S₁, S₂, . . . , S_(M). M groups may be further divided into aplurality of subgroups. The number of subgroups included in each of theM groups is N₁, N₂, . . . , N_(M). In this case, N₁+N₂+ . . . +N_(M)≤Nis satisfied.

The i-th group may be divided into N_(i) subgroups according to thefollowing embodiments. The OFDM symbols included in the i-th group maybe divided into N_(i) subgroups including C_(i)=floor(S_(i)/N_(i)) OFDMsymbols. When S_(i) OFDM symbols are indexed starting from 1 in timeorder, N_(i) subgroups may be represented as follows. The first group is{1, 2, . . . , Ci}, the second group is {C_(i)+1, C_(i)+2, . . . ,2*C_(i)}, the (N_(i)−1)-th group is {(N−2)*C_(i)+1, (N_(i)−2)*C_(i)+2, .. . , (N_(i)−1)*C_(i)}, and the N_(i)-th group is {(N_(i)−1)*C_(i),(N_(i)−1)*C_(i)+1, . . . , S}. In this case, the N_(i)-th group mayinclude more than C_(i) OFDM symbols.

In this case, the number of OFDM symbols included in the Ni subgroups ofthe i-th group may be determined as in the following embodiments. Inmore detail, the number of OFDM symbols included in each of theplurality of subgroups included in the i-th group may be at most one.When Si OFDM symbols are indexed starting from 1 in time order, N_(i)subgroups may be divided as follows. Each of the first mod(S_(i), N_(i))groups of N_(i) groups may include ceil(S_(i)/N_(i)) OFDM symbols, andeach of the other N_(i)−mod(S_(i), N_(i)) groups may includefloor(S_(i)/N_(i)) OFDM symbols.

The number of subgroups included in each of the M groups may bedetermined based on the number of OFDM symbols included in each of the Mgroups. In more detail, the number of subgroups included in each of theM groups may be determined in proportion to the number of OFDM symbolsincluded in each of the M groups. Specifically, the numbers N₁, N₂, . .. N_(M) of subgroups included in each of the M groups may be determinedaccording to the following equation.N ₁=round((N−M)*S ₁ /S)+1,N ₂=round((N−M)*S2/S)+1, . . . ,N _(M−1)=round((N−M)*S _(M−1) /S)+1,N _(M) =N−(N ₁ +N ₂ + . . . +N _(M−1))

In the above equation, the round up operation round(x) may be replacedby floor(x+0.5) indicating a round down operation or ceil(x−0.5)indicating a round up operation.

In another specific embodiment, the numbers N1, N2, . . . NM ofsubgroups included in each of the M groups may be determined accordingto the following equation.N ₁=round(N*S ₁ /S),N ₂=round(N*S ₂ /S), . . . ,N _(M−1)=round(N*S _(M−1) /S),N _(M) =N−(N ₁ +N ₂ + . . . +N _(M−1))

In the above equation, the round up operation round(x) may be replacedby floor(x+0.5) indicating a round down operation or ceil(x−0.5)indicating a round up operation.

In the two embodiments described through the above equation, the orderof groups may be determined according to the order in the time domain ofthe OFDM symbol. Therefore, the first group may include the first S₁OFDM symbols located first and continuous. The M−th group may includeS_(M) OFDM symbols located last and continuous.

According to a specific embodiment, in the two embodiments describedabove through the equation, the order of the groups may be determined inascending order in the time domain of the OFDM symbol. Thus, the firstgroup may include the smallest number of continuous OFDM symbols. TheM−th group may include the largest number of continuous OFDM symbols.According to a specific embodiment, in the two embodiments describedabove through the equation, the order of the groups may be determined indescending order in the time domain of the OFDM symbol. Thus, the firstgroup may include the largest number of continuous OFDM symbols. TheM−th group may include the least number of continuous OFDM symbols. Whenthe number of continuous symbols is the same, the preceding group mayinclude an OFDM symbol located first in the time domain.

In another specific embodiment, when the number of OFDM symbols includedin a subgroup included in each of the M groups is limited to a numbersmaller than C, the numbers N₁, N₂, . . . , N_(M) of subgroups includedin each of the M groups may be determined according to the followingequation.N ₁=ceil(S ₁ /C),N ₂=ceil(S ₂ /C), . . . ,N _(M)=ceil(S _(M) /C)

In this case, C is the smallest number among integers satisfying Σ_(i=1)^(M)ceil(S_(i)/C)≤N. In the above equation, ceil(x) represents a roundup operation.

In another specific embodiment, when the number of OFDM symbols includedin a subgroup included in each of the M groups is limited to a numbersmaller than C, the numbers N₁, N₂, . . . , N_(M) of subgroups includedin each of the M groups may be determined according to the followingequation.N ₁=ceil(S ₁ /C)+a1,N ₂=ceil(S ₂ /C)+a2, . . . ,N _(M)=ceil(S _(M) /C)+a _(M),

In this case, C is the smallest number among integers satisfying Σ_(i=1)^(M)ceil(S_(i)/C)≤N. In the above equation, ceil(x) represents a roundup operation. In addition, the value of a_(i) in the above equation maybe determined by the following equation.a _(i)=1 if i=1, . . . ,N−Σ _(i=1) ^(M)ceil(S _(i) /C),a _(i)=0 if i=Σ _(i=1) ^(M)ceil(S _(i) /C)+1, . . . ,M,

The indexing of the M groups can be configured to satisfy the followingequation.S ₁ ≥S ₂ ≥ . . . ≥S _(M)

In this case, if the number of OFDM symbols included in the groups arethe same, a low index may be allocated to the group including the OFDMsymbols located first in the time domain. The number of OFDM symbolsincluded in the subgroups included in each of the M groups may belimited to less than C, and the number of OFDM symbols included in thesubgroups of the group including more OFDM symbols may be furtherlowered.

In another specific embodiment, the indexing of the M groups can beconfigured to satisfy the following equation.S ₁/(ceil(S ₁ /C))≥S ₂/(ceil(S ₂ /C))≥ . . . ≥S _(M)/(ceil(S _(M) /C))

In this case, when the number of OFDM symbols included in the groups arethe same, a low index may be allocated to the group including the OFDMsymbols located first in the time domain. The number of OFDM symbolsincluded in the subgroups included in each of the M groups may belimited to less than C, and the number of OFDM symbols included in thesubgroups of the group including more OFDM symbols may be furtherlowered.

In another specific embodiment, the indexing of the M groups can beconfigured to satisfy the following equation.ceil(S ₁ /C)≤ceil(S ₂ /C)≤ . . . ≤ceil(S _(M) /C)

In this case, when the number of OFDM symbols included in the groups arethe same, a low index may be allocated to the group including the OFDMsymbols located first in the time domain. The number of OFDM symbolsincluded in the subgroups included in each of the M groups may belimited to less than C, and the number of OFDM symbols included in thesubgroups of the group including more OFDM symbols may be furtherlowered.

In another specific embodiment, the indexing of the M groups can beconfigured to satisfy the following equation.ceil(S ₁ /C)≥ceil(S ₂ /C)≥ . . . ≥ceil(S _(M) /C)

In this case, when the number of OFDM symbols included in the groups arethe same, a low index may be allocated to the group including the OFDMsymbols located first in the time domain. The number of OFDM symbolsincluded in the subgroups included in each of the M groups may belimited to less than C, and the number of OFDM symbols included in thesubgroups of the group including more OFDM symbols may be furtherlowered.

In the above equation, the round up operation round(x) may be replacedby floor(x+0.5) indicating a round down operation or ceil(x−0.5)indicating a round up operation.

As described above, the reference DL resource indicated by thepreemption indicator may include all PRBs of the BWP. The preemptionindicator may divide the reference DL resource into 14 parts andindicate whether a preemption occurs in 14 parts by using a bitmaphaving 14 bits. As described above, the reference DL resource may bedivided into 14 parts in the time domain. In addition, the reference DLresource may be divided into seven parts in the time domain and twoparts in the frequency domain. In addition, the period in which the UEmonitors the preemption indicator may be any one of one slot, two slots,and four slots.

When the UE is configured to perform carrier aggregation (CA) thataggregates a plurality of component carriers, the UE may monitor apreemption indicator indicating preemption information of anothercarrier in one carrier. In this case, the preemption indicator isreferred to as a cross-carrier DL preemption indicator. A transmissionperiod of the preemption indicator will be described in detail withreference to FIG. 30.

FIG. 30 shows that when a CA is configured to a UE according to anembodiment of the present invention, the UE monitors a preemptionindicator indicating information on preemption occurring in anothercarrier in one carrier.

The embodiments of FIGS. 30(a) and 30(b) are for the case where the UEis configured to monitor the preemption indicator in a cell with asubcarrier spacing of 60 KHz, and the preemption indicator is configuredto indicate information on preemption occurring in a cell with asubcarrier spacing of 15 KHz. According to the relationship between theOFDM symbol position of CORESET for monitoring the preemption indicatorin the cell having a subcarrier spacing of 60 KHz and the position ofthe OFDM symbol of a cell having a subcarrier spacing of 15 KHz, theOFDM symbol corresponding to the reference DL resource may be three orfour OFDM symbols. Specifically, when the symbol position of CORESET formonitoring the preemption indicator in a cell with a subcarrier spacingof 60 KHz starts at the first or second OFDM symbol position of a cellwith a subcarrier spacing of 15 KHz, the OFDM symbol corresponding tothe reference DL resource may be four OFDM symbols. In addition, whenthe symbol position of CORESET for monitoring the preemption indicatorin a cell with a subcarrier spacing of 60 KHz starts at the third orfourth OFDM symbol position of a cell with a subcarrier spacing of 15KHz, the OFDM symbol corresponding to the reference DL resource may bethree OFDM symbols. In such a way, according to the relationship betweenthe OFDM symbol position of CORESET for monitoring the preemptionindicator in the cell having a subcarrier spacing of 60 KHz and theposition of the OFDM symbol of a cell having a subcarrier spacing of 15KHz, the number of OFDM symbols corresponding to the reference DLresource may vary. In addition, the number of OFDM symbols between thepreemption indicator monitoring periods may be represented byN_symb*T_INT*2^((μ-μ_INT)). In this case, N_symb is the number of OFDMsymbols included in the slot. When a normal cyclic prefix (CP) is used,N_symb is 14. When an extended CP is used, N_symb is 12. In addition,T_INT is a monitoring period of the preemption indicator. In addition,T_INT may be one of 1, 2, and 4. μ_INT is a value satisfying that thesubcarrier spacing of the carrier in which the DL preemption indicatoris transmitted is 15*2^(μ_INT) KHz. μ is a value satisfying that thesubcarrier spacing of the carrier in which the preemption indicatorindicates information on the preemption is 15*2^(μ) KHz.

The base station may signal the preemption indicator in an integernumber of slot periods. The base station may signal the preemptionindicator in an integer number of slot periods. The base station mayconfigure a value of T_INT, a value of μ, and a value of μ_INT, throughwhich T_INT*2^((μ-μ_INT)) is a natural number, and signal thecorresponding value to the UE. The UE may expect the value of T_INT, thevalue of μ, and the value of μ_INT, through which T_INT*2^((μ-μ_INT)) isa natural number. The UE may not expect a value of T_INT, a value of μ,and a value of μ_INT through which T_INT*2^((μ-μ_INT)) becomes a decimalpoint number. According to a specific embodiment, when the value ofT_INT*2^((μ-μ_INT)) is a decimal point number, the UE may ignore thevalue of T_INT. Alternatively, when the UE receives a value of T_INT, avalue of μ, and a value of μ_INT through which the value ofT_INT*2^((μ-μ_INT)) becomes a decimal point number, the UE may determinethe corresponding configuration from the base station as an error case.In this case, the UE may not perform any operation. Alternatively, whenthe UE receives a value of T_INT, a value of μ, and a value of μ_INTthrough which the value of T_INT*2^((μ-μ_INT)) becomes a decimal pointnumber, the UE may not perform monitoring to receive the preemptionindicator from the base station. In more detail, the UE does not expect(T_INT, μ, μ_INT)=(1,0,1), (T_INT, μ, μ_INT)=(1,0,2) or (T_INT, μ,μ_INT)=(2,0,2). The base station may configure the values of T_INT, μ,and μ_INT that make T_INT*2^((μ-μ_INT)) is a natural number.

In addition, the UE can expect the value of T_INT, the value of μ, andthe value of μ_INT through which N_symb*T_INT*2^((μ-μ_INT)) is a naturalnumber. The UE may not expect a value of T_INT, a value of μ, and avalue of μ_INT through which N_symb*T_INT*2^((μ-μ_INT)) becomes adecimal point number. According to a specific embodiment, when the valueof N_symb*T_INT*2T_INT*2^((μ-μ_INT)) is a decimal point number, the UEmay ignore the value of T_INT. Alternatively, when the UE receives avalue of T_INT, a value of μ, and a value of μ_INT through which thevalue of T_INT*2^((μ-μ_INT)) becomes a decimal point number, the UE maydetermine the corresponding configuration as an error case. In thiscase, the UE may not perform any operation. Alternatively, when the UEreceives a value of T_INT, a value of μ, and a value of μ_INT throughwhich the value of T_INT*2^((μ-μ_INT)) becomes a decimal point number,the UE may not perform monitoring to receive the preemption indicatorfrom the base station. For example, when N_symb=14, the UE does notexpect (T_INT, μ, μ_INT)=(2,0,2). The base station may configure thevalues of T_INT, μ, and μ_INT that make N_symb*T_INT*2^((μ-μ_INT)) is anatural number.

In addition, the UE can expect that the μ value is greater than or equalto the μ_INT value. In more detail, the preemption indicator may alwaysbe transmitted in a carrier with a subcarrier spacing smaller than thatof a carrier indicated by the preemption indicator. For example, apreemption indicator indicating information on a preemption of a carrierwith a 15 kHz subcarrier spacing, a carrier with a 30 kHz subcarrierspacing, and a carrier with a 60 kHz subcarrier spacing may betransmitted in a carrier with a 15 kHz subcarrier spacing. In thecarrier with 30 kHz subcarrier spacing, a preemption indicatorindicating information on the preemption of the carrier with 30 kHzsubcarrier spacing and the carrier with 60 kHz subcarrier spacing may betransmitted. In a carrier with a 60 kHz subcarrier spacing, a preemptionindicator indicating information on a preemption of a carrier with a 60kHz subcarrier spacing may be transmitted. In a carrier with a 30 kHzsubcarrier spacing, a preemption indicator indicating information on apreemption of a carrier with a 15 kHz subcarrier spacing may not betransmitted. In the carrier with 60 kHz subcarrier spacing, a preemptionindicator indicating information on the preemption of the carrier with15 kHz subcarrier spacing and the carrier with 30 kHz subcarrier spacingmay not be transmitted.

Although the case where the UE is configured to perform CA in FIG. 30has been described as an example, the embodiment described withreference to FIG. 30 may also be applied to the case where the UEoperates in one cell (or carrier). In more detail, when a plurality ofBWPs configured as different subcarrier configurations are used for theUE and the UE is configured to monitor the preemption indicator inanother BWP in one BWP, the above-described embodiments may be applied.

FIGS. 31 to 32 show a method of operating a base station and a UEaccording to an embodiment of the present invention.

The base station generates a preemption indicator indicating a preempted(or punctured) resource (S3101). The base station transmits a preemptionindicator to the UE on the basis of a predetermined period (S3103). Inmore detail, the base station may transmit a preemption indicator at atime point corresponding to a predetermined period. In this case, thebase station may signal a predetermined period to the UE.

The preemption indicator may indicate information on the remaining OFDMsymbols except some of the OFDM symbols included in the slot indicatedby the preemption indicator. In more detail, the reference resourceindicated by the preemption indicator may not include an OFDM symbolconfigured as a UL symbol. In this case, the UL symbol may be configuredin the RRC signal. In more detail, the RRC signal may be a cell-specificRRC signal. In addition, the preemption indicator may indicate onlyinformation on a resource corresponding to a DL symbol or a flexiblesymbol that is able to be configured as a DL symbol. The referenceresource indicated by the preemption indicator may be determinedaccording to the embodiments described with reference to FIGS. 21through 26.

In addition, the preemption indicator may divide a plurality of OFDMsymbols indicated by the preemption indicator into a plurality ofgroups, and indicate whether a plurality of groups are punctured in atleast one OFDM symbol among one or more OFDM symbols included in each ofthe plurality of groups. In this case, the number of the plurality ofgroups may be specified in advance. In more detail, the number of theplurality of groups may be the number of bits of the bitmap included inthe preemption indicator. In another specific embodiment, the number ofgroups may be determined according to the OFDM symbol granularityconfigured by the base station.

When the number of the plurality of groups is N and the number of theplurality of OFDM symbols indicated by the preemption indicator is S,the base station may group the first mod(S, N) groups among the N groupsto include ceil(S/N) OFDM symbols, and group the remaining N−mod(S, N)groups to include floor(S/N) OFDM symbols. In this case, mod(a, b) maybe a−floor(a/b)*b, floor(x) may be the largest number among integersless than or equal to x, and ceil(x) may be the smallest of integersgreater than or equal to x. In a specific embodiment, the base stationmay group a plurality of groups indicated by the preemption indicatoraccording to the embodiments described with reference to FIGS. 27 to 29.

The UE may monitor the preemption indicator in units of integer slots.Accordingly, the base station may transmit the preemption indicator toallow the UE to monitor the preemption indicator in units of integerslots. In more detail, the number of OFDM symbols between predeterminedperiods may be represented by N_symb*T_INT*2^((μ-μ_INT)). In this case,N_symb may be the number of OFDM symbols included in the slot. Inaddition, T_INT may be a period in which the UE monitors the preemptionindicator. In addition, μ_INT may be a value satisfying that thesubcarrier spacing of the carrier in which the preemption indicator istransmitted becomes 15*2^(μ_INT) KHz. In addition, μ may be a value thatsatisfies that the subcarrier spacing of the carrier in which thepreemption indicator indicates information on the preemption becomes15*2^(μ) KHz. Accordingly, the base station may configure the values ofT_INT, μ, and μ_INT that make N_symb*T_INT*2^((μ-μ_INT)) is a naturalnumber. In a specific embodiment, the base station may configure valuesof T_INT, μ, and μ_INT according to the embodiments described withreference to FIG. 30.

In addition, the preemption indicator may indicate the entire band ofthe BWP used by the UE. In a specific embodiment, the base station maytransmit the preemption indicator according to the embodiments describedwith reference to FIGS. 12 to 20.

The UE periodically monitors a preemption indicator indicating apreempted (or punctured) resource (S3201). When the UE receives thepreemption indicator, the UE determines a preempted resource amongresources scheduled for the UE based on the preemption indicator(S3203). In more detail, the UE may assume that the transmission is notperformed in a resource indicated as a preempted resource amongresources scheduled for the UE. In addition, the UE may receive thepreemption indicator to determine a resource in which the preemption forto UE occurs by the base station according to the value of thepreemption indicator. Accordingly, the UE may determine whethertransmission from the base station occurs in the resource indicated bythe preemption among the scheduled resources. In more detail, the UE maydetermine, using the value of the bits included in the preemptionindicator, whether transmission from the base station to the UE occursin at least one OFDM symbol corresponding to each bit of the preemptionindicator. For example, when the value of one of the bits included inthe preemption indicator is the first value, the UE may determine thattransmission from the base station to the UE occurs in at least one OFDMsymbol corresponding to the corresponding bit. In addition, when thevalue of one of the bits included in the preemption indicator is thesecond value, the UE may determine that transmission from the basestation to the UE does not occur in at least one OFDM symbolcorresponding to the corresponding bit. The UE may decode data receivedfrom the base station based on the resource in which the transmissionfrom the base station to the UE occurs. In this case, the data mayinclude at least one of a data channel and a control channel. Thepreemption indicator may indicate information on the remaining OFDMsymbols except some of the OFDM symbols included in the slot indicatedby the preemption indicator. Accordingly, the UE may determine that theUE indicates information on the remaining OFDM symbols except for somesymbols among the OFDM symbols included in the slot indicated by thepreemption indicator. In more detail, the UE may determine a resourceindicated by the preemption indicator based on the OFDM symbolconfiguration included in the slot indicated by the preemptionindicator. In more detail, the UE may determine that a resourceindicated by the preemption indicator does not include an OFDM symbolconfigured as a UL symbol. In this case, the UL symbol may be configuredby the RRC signal. In more detail, the RRC signal may be a cell-specificRRC signal. In addition, the UE may determine that the preemptionindicator indicates only information on a resource corresponding to a DLsymbol or a flexible symbol that may be a DL symbol. In another specificembodiment, the UE may determine the resource indicated by thepreemption indicator based on the information on the OFDM symbolindicated through the preemption indicator. In this case, the UE mayobtain information on the OFDM symbol indicated by the preemptionindicator from the RRC signal. In a specific embodiment, the UE maydetermine the resource indicated by the preemption indicator accordingto the embodiments described with reference to FIGS. 21 to 26.

In addition, the preemption indicator may divide a plurality of OFDMsymbols indicated by the preemption indicator into a plurality ofgroups, and indicate whether a plurality of groups are punctured orpreempted in at least one OFDM symbol among one or more OFDM symbolsincluded in each of the plurality of groups. In this case, the UE maydetermine that the transmission from the base station to the UE occursor does not occur in all of one or more OFDM symbols included in a groupcorresponding to one bit. In more detail, when a value of a bit is thefirst value, the UE may determine that transmission from the basestation to the UE occurs in all one or more OFDM symbols included in thegroup corresponding to the bit. In addition, when a value of a bit isthe second value, the UE may determine that transmission does not occurin all of one or more OFDM symbols included in the group correspondingto the bit. In addition, the number of the plurality of groups may bespecified in advance. In more detail, the number of the plurality ofgroups may be the number of bits of the bitmap included in thepreemption indicator. In another specific embodiment, the number ofgroups may be determined according to the OFDM symbol granularityconfigured by the base station.

When the number of the plurality of groups is N and the number of theplurality of OFDM symbols indicated by the preemption indicator is S, itis determined that the UE may group the first mod(S, N) groups among theN groups to include ceil(S/N) OFDM symbols, and group the remainingN−mod(S, N) groups to include floor(S/N) OFDM symbols. In this case,mod(a, b) may be a−floor(a/b)*b, floor(x) may be the largest numberamong integers less than or equal to x, and ceil(x) may be the smallestof integers greater than or equal to x. In a specific embodiment, the UEmay determine that a plurality of groups indicated by the preemptionindicator are grouped according to the embodiments described withreference to FIGS. 27 to 29.

The UE may monitor the preemption indicator in units of integer slots.In more detail, the number of OFDM symbols between predetermined periodsmay be represented by N_symb*T_INT*2^((μ-μ_INT)). In this case, N_symbmay be the number of OFDM symbols included in the slot. In addition,T_INT may be a period in which the UE monitors the preemption indicator.In addition, μ_INT may be a value satisfying that the subcarrier spacingof the carrier in which the preemption indicator is transmitted becomes15*2^(μ_INT) KHz. In addition, μ may be a value that satisfies that thesubcarrier spacing of the carrier in which the preemption indicatorindicates information on the preemption becomes 15*2^(μ) KHz.Accordingly, the UE can expect values of T_INT, μ, and μ_INT that make avalue of N_symb*T_INT*2^((μ-μ_INT)) a natural number. The UE may ignorevalues of T_INT, μ, and μ_INT that makes N_symb*T_INT*2^((μ-μ_INT)) anon-natural value. Alternatively, when the UE receives values of T_INT,μ, and μ_INT that make T_INT*2^((μ-μ_INT)) a decimal point number, theUE may determine the corresponding configuration as an error case. Inthis case, the UE may not perform any operation. Alternatively, when theUE receives values of T_INT, μ, μ_INT that make the value ofT_INT*2^((μ-μ_INT)) a decimal point number, the UE may not performmonitoring to receive the preemption indicator from the base station. Ina specific embodiment, the UE may expect values of T_INT, μ, and μ_INTaccording to the embodiments described with reference to FIG. 30.

The above-mentioned description of the present invention is forillustrative purposes only, and it will be understood that those ofordinary skill in the art to which the present invention belongs maymake changes to the present invention without altering the technicalideas or essential characteristics of the present invention and theinvention may be easily modified in other specific forms. Therefore, theembodiments described above are illustrative and are not restricted inall aspects. For example, each component described as a single entitymay be distributed and implemented, and likewise, components describedas being distributed may also be implemented in an associated fashion.

The scope of the present invention is defined by the appended claimsrather than the above detailed description, and all changes ormodifications derived from the meaning and range of the appended claimsand equivalents thereof are to be interpreted as being included withinthe scope of present invention.

The invention claimed is:
 1. A base station of a wireless communicationsystem using a time division duplex (TDD), scheme, the base stationcomprising: a communication module; and a processor configured tocontrol the communication module, wherein the processor is configuredto: generate a preemption indicator indicating a preempted resourcewithin a predetermined period which includes a first plurality oforthogonal frequency division multiplexing (OFDM) symbols which compriseuplink (UL) symbols for uplink transmission, downlink (DL) symbols fordownlink transmission, and flexible symbols configured as neither a ULsymbol nor a DL symbol, wherein the UL symbols, the DL symbols, and theflexible symbols are configured by the base station, transmit thepreemption indicator to a user equipment of the wireless communicationsystem based on the predetermined period, wherein the preemptionindicator indicates a preempted resource among a second plurality ofOFDM symbols which are OFDM symbols included in the first plurality ofOFDM symbols except for a UL symbol configured by a cell-specific radioresource control (RRC), signal.
 2. The base station of claim 1, whereinthe preemption indicator divides the second plurality of OFDM symbolsinto a plurality of groups, and indicates whether at least one OFDMsymbols is preempted in one or more OFDM symbols included in each of theplurality of groups for each of the plurality of groups.
 3. The basestation of claim 2, wherein a number of the plurality of groups ispredetermined.
 4. The base station of claim 2, wherein a number of theplurality of groups is N, wherein a number of the second plurality ofOFDM symbols is S, wherein the processor is configured to group a firstmod(S, N) groups among N groups such that each of the first mod(S, N)groups includes ceil(S/N) OFDM symbols and groups remaining N—mod(S, N)groups such that each of the N—mod(S, N) groups includes floor(S/N) OFDMsymbols, wherein the mod(a, b) represents a—floor(a/b)*b, wherein thefloor(x) represents a largest integer less than or equal to x, whereinthe ceil(x) represents a smallest integer number greater than or equalto x.
 5. The base station of claim 1, wherein a number of the firstplurality of OFDM symbols between the predetermined periods isN_symb*T_INT*2^((μ-μ_INT)), wherein N_symb represents a number of OFDMsymbols included in a slot, wherein T_INT represents a periodicity ofmonitoring the preemption indicator, wherein μ_INT represents a valuesatisfying that a subcarrier spacing of a carrier through which thepreemption indicator is transmitted is 15*2^(μ_INT) KHz, wherein μrepresents a value satisfying that a subcarrier spacing of a carrierwhich are indicated by the preemption indicator is 15*2^(μ) KHz, whereinthe processor is configured to configure values of T_INT, μ, and μ_INTthat makes a value of N_symb*T_INT*2^((μ-μ_INT)) a natural number. 6.The base station of claim 1, wherein the preemption indicator indicatesa full bandwidth of a bandwidth part (BWP) used by the user equipment,wherein the BWP is equal to or narrower than a bandwidth configured tothe user equipment and is a frequency band through which the userequipment performs transmission and/or reception.
 7. A user equipment ofa wireless communication system using a time division duplex (TDD)scheme, the user equipment comprising: a communication module; and aprocessor configured to control the communication module, wherein theprocessor is configured to: periodically monitor a preemption indicatorwithin a predetermined period which includes a first plurality oforthogonal frequency division multiplexing (OFDM) symbols which comprise(UL) symbols for uplink transmission, downlink (DL) symbols for downlinktransmission, and flexible symbols configured as neither a UL symbol nora DL symbol, wherein the UL symbols, the DL symbols, and the flexiblesymbols are configured by a base station of the wireless communicationsystem, when receiving the preemption indicator, determine a secondplurality of OFDM symbols among which the preemption indicator indicatesa preempted resource, wherein the second plurality of OFDM symbols areOFDM symbols included in the first plurality of OFDM symbols except fora UL symbol configured by a cell-specific radio resource control (RRCsignal), when receiving the preemption indicator, determine a resourcein which transmission from the base station to the user equipment occursamong resources scheduled to the user equipment based on the preemptionindicator, and decode received data from the base station based on thedetermined resource.
 8. The user equipment of claim 7, wherein thepreemption indicator divides the second plurality of OFDM symbols into aplurality of groups, wherein the processor is configured to determine,for each of the plurality of groups, that transmission from the basestation is performed in one or more OFDM symbols which are included inthe each of the plurality of groups.
 9. The user equipment of claim 8,wherein a number of the plurality of groups is predetermined.
 10. Theuser equipment of claim 8, wherein a number of the plurality of groupsis N, wherein a number of the second plurality of OFDM symbols is S,wherein the processor is configured to determine that each of a firstmod(S, N) groups among N groups includes ceil(S/N) OFDM symbols and eachof remaining N—mod(S, N) groups includes floor(S/N) OFDM symbols,wherein the mod(a, b) represents a—floor(a/b)*b, wherein the floor(x)represents a largest integer less than or equal to x, wherein theceil(x) represents a smallest integer number greater than or equal to x.11. The user equipment of claim 7, wherein a number of the firstplurality of OFDM symbols between periods of monitoring the preemptionindicator is N_symb*T_INT*2^((μ-μ_INT)), wherein N_symb represents anumber of OFDM symbols included in a slot, wherein T_INT represents aperiodicity of monitoring the preemption indicator, wherein μ_INTrepresents a value satisfying that a subcarrier spacing of a carrierthrough which the preemption indicator is transmitted is 15*2^(μ_INT)KHz, wherein μ represents a value satisfying that a subcarrier spacingof a carrier which are indicated by the preemption indicator is 15*2^(μ)KHz, wherein the processor is configured to expect values of T_INT, μ,and μ_INT that make a value of N_symb*T_INT*2^((μ-μ_INT)) a naturalnumber.
 12. The user equipment of claim 7, wherein the preemptionindicator indicates a full bandwidth of a bandwidth part (BWP) used bythe user equipment, wherein the BWP is equal to or narrower than abandwidth configured to the user equipment and is a frequency bandthrough which the user equipment performs transmission and/or reception.13. A method of operating a user equipment of a wireless system using atime division duplex (TDD), scheme, the method comprising: periodicallymonitoring a preemption indicator within a predetermined period whichincludes a first plurality of orthogonal frequency division multiplexing(OFDM) symbols which comprise uplink (UL) symbols for uplinktransmission, downlink (DL) symbols for downlink transmission, andflexible symbols configured as neither a UL symbol nor a DL symbol,wherein the UL symbols, the DL symbols, and the flexible symbols areconfigured by a base station of the wireless communication system, whenreceiving the preemption indicator, determining a second plurality ofOFDM symbols among which the preemption indicator indicates a preemptedresource, wherein the second plurality of OFDM symbols are OFDM symbolsincluded in the first plurality of OFDM symbols except for a UL symbolconfigured by a cell-specific radio resource control (RRC) signal, whenreceiving the preemption indicator, determining a resource in whichtransmission from the base station to the user equipment occurs amongresources scheduled to the user equipment based on the preemptionindicator, and decoding data received from the base station based on thedetermined resource.
 14. The method of claim 13, wherein the preemptionindicator divides the first plurality of OFDM symbols into a pluralityof groups, wherein the determining the resource in which thetransmission from the base station to the user equipment occurscomprises determining whether transmission from the base station to theuser equipment occurs in at least one OFDM symbol included in each ofthe plurality of groups for each of the plurality of groups.